电子 电流 外文翻译 外文文献 英文文献 高度稳压直流电源

中英文对照外文翻译文献(文档含英文原文和中文翻译)外文文献：DC Motor CalculationsOverviewNow that we have a good understanding of dc generators, we can begin our study of dc motors. Direct-current motors transform electrical energy into mechanical energy. They drive devices such as hoists, fans, pumps, calendars, punch-presses, and cars. These devices may have a definite torque-speed characteristic (such as a pump or fan) or a highly variable one (such as a hoist or automobile). The torque-speed characteristic of the motor must be adapted to the type of the load it has to drive, and this requirement has given rise to three basic types of motors: 1.Shunt motors 2. Series motors 3. Compound motors Direct-current motors are seldom used in ordinary industrial applications because all electric utility systems furnish alternating current. However, for special applications such as in steel mills, mines, and electric trains, it is sometimes advantageous to transform the alternating current into direct current in order to use dc motors. The reason is that the torque-speed characteristics of dc motors can be varied over a wide range while retaining high efficiency. Today, this general statement can be challenged because the availability of sophisticated electronic drives has made it possible to use alternating current motors for variable speed applications. Nevertheless, there are millions of dc motors still in service and thousands more are being produced every year.Counter-electromotive force (cemf)Direct-current motors are built the same way as generators are; consequently, a dc machine can operate either as a motor or as a generator. To illustrate, consider a dc generator in which the armature, initially at rest, is connected to a dc source E s by means of a switch (Fig. 5.1). The armature has a resistance R, and the magnetic field is created by a set of permanent magnets.As soon as the switch is closed, a large current flows in the armature because its resistance is very low. The individual armature conductors are immediately subjected to a force because they are immersed in the magnetic field created by the permanent magnets. These forces add upto produce a powerful torque, causing the armature to rotate.Figure 5.1 Starting a dc motor across the line.On the other hand, as soon as the armature begins to turn, a second phenomenon takes place: the generator effect. We know that a voltage E o is induced in the armature conductors as soon as they cut a magnetic field (Fig. 5.2). This is always true, no matter what causes the rotation. The value and polarity of the induced voltage are the same as those obtained when the machine operates as a generator. The induced voltage E o is therefore proportional to the speed of rotation n of the motor and to the flux F per pole, as previously given by Eq. 5.1:E o = Zn F/60 (5.1)As in the case of a generator, Z is a constant that depends upon the number of turns on the armature and the type of winding. For lap windings Z is equal to the number of armature conductors.In the case of a motor, the induced voltage E o is called counter-electromotive force (cemf) because its polarity always acts against the source voltage E s. It acts against the voltage in the sense that the net voltage acting in the series circuit of Fig. 5.2 is equal to (E s - Eo) volts and not (E s + E o) volts.Figure 5.2 Counter-electromotive force (cemf) in a dc motor.Acceleration of the motorThe net voltage acting in the armature circuit in Fig. 5.2 is (E s- E o) volts. The resulting armature current /is limited only by the armature resistance R, and soI = (E s- E o)IR (5.2)When the motor is at rest, the induced voltage E o= 0, and so the starting current isI = E s/RThe starting current may be 20 to 30 times greater than the nominal full-load current of the motor. In practice, this would cause the fuses to blow or the circuit-breakers to trip. However, if they are absent, the large forces acting on the armature conductors produce a powerful starting torque and a consequent rapid acceleration of the armature.As the speed increases, the counter-emf E o increases, with the result that the value of (E s—E o)diminishes. It follows from Eq. 5.1 that the armature current / drops progressively as the speed increases.Although the armature current decreases, the motor continues to accelerate until it reaches a definite, maximum speed. At no-load this speed produces a counter-emf E o slightly less than the source voltage E s. In effect, if E o were equal to E s the net voltage (E s—E o) would become zero and so, too, would the current /. The driving forces would cease to act on the armature conductors, and the mechanical drag imposed by the fan and the bearings would immediately cause the motor to slow down. As the speed decreases the net voltage (E s—E o) increases and so does the current /. The speed will cease to fall as soon as the torque developed by the armature current is equal to the load torque. Thus, when a motor runs at no-load, the counter-emf must be slightly less than E s so as to enable a small current to flow, sufficient to produce the required torque.Mechanical power and torqueThe power and torque of a dc motor are two of its most important properties. We now derive two simple equations that enable us to calculate them.1. According to Eq. 5.1 the cemf induced in a lap-wound armature is given byE o = Zn F/60Referring to Fig. 5.2, the electrical power P a supplied to the armature is equal to the supply voltage E s multiplied by the armature current I:P a = E s I (5.3)However, E s is equal to the sum of E o plus the IR drop in the armature:E s = E o + IR (5.4)It follows thatP a= E s I= (E o + IR)I=E o I + I2R (5.5)The I2R term represents heat dissipated in the armature, but the very important term E o I is the electrical power that is converted into mechanical power. The mechanical power of the motor is therefore exactly equal to the product of the cemf multiplied by the armature currentP = E o I (5.6)whereP = mechanical power developed by the motor [W]E o= induced voltage in the armature (cemf) [V]I = total current supplied to the armature [A]2. Turning our attention to torque T, we know that the mechanical power P is given by the expressionP = nT/9.55 (5.7)where n is the speed of rotation.Combining Eqs. 5.7,5.1, and 5.6, we obtainnT/9.55 = E o I= ZnFI/60and soT =Z F I/6.28The torque developed by a lap-wound motor is therefore given by the expressionT =Z F I/6.28 (5.8)whereT = torque [N×m]Z = number of conductors on the armatureF = effective flux per pole [Wb]*/ = armature current [A]6.28 = constant, to take care of units[exact value = 2p]Eq. 5.8shows that we can raise the torque of a motor either by raising the armature current or by raising the flux created by the poles.Speed of rotationWhen a dc motor drives a load between no-load and full-load, the IR drop due to armature resistance is always small compared to the supply voltage E s. This means that the counter-emf E s is very nearly equal to E s.On the other hand, we have already seen that Eo may be expressed by the equationE o = Zn F/60Replacing E o by E s we obtainE s = Zn F/60That is,wheren = speed of rotation [r/min]E s = armature voltage [V]Z = total number of armature conductorsThis important equation shows that the speed of the motor is directly proportional to the armature supply voltage and inversely proportional to the flux per pole. We will now study how this equation is applied.Armature speed controlAccording to Eq. 5.8, if the flux per pole F is kept constant (permanent magnet field or field with fixed excitation), the speed depends only upon the armature voltage E s. By raising or lowering E s the motor speed will rise and fall in proportion.In practice, we can vary E s by connecting the motor armature M to a separately excited variable-voltage dc generator G . The field excitation of the motor is kept constant, but the generator excitation I x can be varied from zero to maximum and even reversed. The generator output voltage E s can therefore be varied from zero to maximum, with either positive or negative polarity. Consequently, the motor speed can be varied from zero to maximum in either direction. Note that the generator is driven by an ac motor connected to a 3-phase line. This method of speed control, known as the Ward-Leonard system, is found in steel mills, high-rise elevators, mines, and paper mills.In modem installations the generator is often replaced by a high-power electronic converter that changes the ac power of the electrical utility to dc, by electronic means.What happens to the dc power received by generator G? When G receives electric power, it operates as a motor, driving its own ac motor as an asynchronous generator!* As a result, ac power is fed back into the line that normally feeds the ac motor. The fact that power can be recovered this way makes the Ward-Leonard system very efficient, and constitutes another of its advantages.Rheostat Speed ControlAnother way to control the speed of a dc motor is to place a rheostat in series with the armature . The current in the rheostat produces a voltage drop which subtracts from the fixed source voltage E s, yielding a smaller supply voltage across the armature. This method enables us to reduce the speed below its nominal speed. It is only recommended for small motors because a lot of power and heat is wasted in the rheostat, and the overall efficiency is low. Furthermore, thespeed regulation is poor, even for a fixed setting of the rheostat. In effect, the IR drop across the rheostat increases as the armature current increases. This produces a substantial drop in speed with increasing mechanical load.中文译文：直流电动机的计算概述现在，我们对直流发电机有一个很好的了解，我们可以开始对直流电动机的研究了。

英文翻译及文献电子电子功率半导体I. IntroductionSolid state semiconductor switches are very inviting to use at pulsed power systems because these switches have high reliability, long lifetime, low costs during using, and environmental safety due to mercury and lead are absent. Semiconductor switches are able to work in any position, so, it is possible to design systems as for stationary laboratory using, and for mobile using. Therefore these switches are frequently regarded as replacement of gas-discharge devices – ignitrons, thyratrons, spark gaps and vacuum switches that generally use now in high-power electrophysical systems including power lasers.Traditional thyristors (SCR) are semiconductor switches mostly using for pulse devices. SCR has small value of forward voltage drop at switch-on state, it has high overload capacity for current, and at last it has relatively low cost value due to the simple bipolar technology. Disadvantage of SCR is observed at switching of current pulses with very high peak value and short duration. Reason of this disadvantage is sufficiently slow process of switch-on state expansion from triggering electrode to external border of p-n junction after triggering pulse applying. This SCR feature is defined SCR using into millisecond range of current switching. Improvement of SCR pulse characteristics can be reached by using of the distributed gate design. This is allowed to decrease the time of total switch-on and greatly improve SCR switching capacity. Thus, ABB company is expanded the semiconductor switch using up to microsecond range by design of special pulse asymmetric thyristors (ASCR). These devices have distributing gate structure like a GTO. This thyristor design and forced triggering mode are obtained the high switching capacity of thyristor (p I =150kA, p T =50μs, di/dt = 18kA/μs, single pulse). However, in this design gate structure is covered large active area of thyristor (more than 50%) that decrease the efficiency of Si using and increase cost of device.Si-thyristors and IGBT have demonstrated high switching characteristics at repetitive mode. However, such devices do not intend for switching of high pulse currents (tens of kiloamperes and more) because of well-known physical limits are existed such as low doping of emitters, short lifetime of minority carriers, small sizes of chips etc.Our investigation have obtained that switches based on reverse – switched dinistors are more perspective solid-state switches to switch super high powers at microsecond and submillisecond ranges. Reverse –switched dinistors (RSD) is two-electrode analogue of reverse conducting thyristor with monolithical integrated freewheeling diode in Si. This diode is connected in parallel and in the back direction to the thyristor part of RSD. Triggering of RSD is provided by short pulse of trigger current at brief applying of reversal voltage to RSD. Design of RSD is made thus that triggering current passes through diode areas of RSD quasiaxially and uniformly along the Si structure area. This current produces the oncoming injection of charge carriers from both emitter junctions to base regions and initiates the regenerative process of switch-on for RSD thyristor areas. Such method of triggering for this special design of Si plate is provided total and uniform switching of RSD along all active area in the very short time like as diode switch-on. The freewheeling diode integrated into the RSD structure could be used as damping diode at fault mode in the discharge circuit. This fault mode such as breakdown of cable lines can lead to oscillating current through switch..It has been experimentally obtained in that semiconductor switches based on RSD can work successfully in the pulsed power systems to drive flash lamps pumping high-power neodymium lasers. It was shown in that RSD-switches based on RSD wafer diameter of 63 mm (switch type KRD-25-100) and RSD-switches based on RSD wafer diameter of 76 mm (switch type KRD-25-180) can switch the current pulses with submillisecond duration and peak value of 120 kA and 180 kA respectively. Three switches (switch type KRD – 25-180) connected in parallel were successfully tested under the following mode: operating voltage V= 25 kV, operating current Ip = 470 kA, and transferred charge Q = 145 Coulombs.oDuring 2000 – 2001, the capacitor bank for neodymium laser of facility LUCH was built at RFNC-VNIIEF. This bank including 18 switches type KRD-25-100 operates successfully during 5 years without any failures of switches.This report is submitted results of development of new generation of solid state switches having low losses of power and high-current switching capacity.II. Development of RSD’s next generationThe technology of fabrication of new RSD structure has been developed to increase theswitching capacity. This new structure is SPT (Soft Punch Through)-structure - with “soft” closing of space-charge region into buffer n'-layer.Decreasing of n-base thickness and also improving of RSD switch-on uniformity by good spreading of charge carriers on the n'-layer at voltage inversion are provided decreasing of all components of losses energy such as losses at triggering, losses at transient process of switch-on, and losses at state-on. Our preliminary estimation was shown that such structure must provide the increasing of operating peak current through RSD approximately in 1.5 times.Investigations were carried out for RSD with blocking voltage of 2.4 kV and Si waferdiameters of 63, 76, and 100 mm by special test station. The main goal of these investigations is definition of maximum permissible level of peak current passing through single RSD with given area. Current passing through RSD and voltage drop on RSD structure during current passing are measured at testing. In Fig.1 waveforms of peak currents and voltage drops is shown for RSD with size of 76 mm and blocking voltage of 2.4 kV.Fig.1. Waveforms of pulse current (a) and voltage drop (b) for RSD with wafer size of 76 mm andblocking voltage of 2.4 kVIn according with study program current was slowly increased until maximum permissible level Ipm. When this level was reached the sharp rise of voltage and than thesame sharp decay of voltage for curve U(t) was observed. Reason of voltage rise is strong decreasing of carrier mobility at high temperature, and reason of voltage decay is quick modulation of channel conductivity by thermal generated plasma that is appeared in accordance with sharp exponential dependence for own concentration of initial silicon into base areas of RSD at temperature of 400 – 0600C.Tests were shown that this sharp rise of voltage at maximum permissible current does not lead to immediate fault of RSD. RSD keeps its blocking characteristic. However, after passing of such current pm I we can observe the appearance of erosion from cathode for aluminum metallization of RSD contacts, and this fact is evidence of borderline state of device. The subsequent increasing of current (more than pm I ) leads to fusing of Si structure. Therefore, level Ipm is the reference position to define the value of operation peak current for RSD-switch under long and repeated many times operating mode.We have determined that operating peak current pw I must be less than 80% from level pm I . This ratio was confirmed by calculations and results of tests under pw I mode (several thousands of shots).Data of test results for new generation of RSD with the various diameter of Si wafer are shown in Table 1. In this Table for comparing results of the same tests for the first generation of RSD with size of 63 and 76 mm are shown.III. Switches based on RSD of new generationNew reverse – switched dinistors is manufactured in two variants. RSD of the first variant is in the low-profile metal-ceramic housing. The second variant is RSD fabricated without housing and with additional protection of periphery area from external action.Dinistors placed into housing can be used for work under as mono - pulse mode and repeated - pulse mode. If repeated-pulsed mode using the forced cooling of semiconductor devices and using of heatsinks to both side of pellet must be made. Dinistors without housing connects in series, and such assembly could be placed into a single compact housing. However, such assembly can work under mono-pulse mode only.Operating voltage for switch typically exceeds blocking voltage of single RSD (BO U ≤2400V), thus switch is included several RSDs connected in series. Fig.2. Reverse –switched dinistors for peak current from 200 kA to 500 kA and blocking voltage of 2400 V , encapsullated in hermetic metal – ceramic housing and without housing (RSD sizes of 64, 76, and 100 mm).Number of RSDs included in assembly depends on operating voltage of switch. Therefore, technical problem of switch development is mainly optimization of design for assembly of several dinistors connected in series. A lot of special investigations have carried out such as choice of optimum materials to provide best contacts between RSDs, calculation of dynamic forces to clamp assembly, etc. These investigations are provided small and stable transition electrical and thermal resistances between RSDs that guarantees long and reliable performance of switch. Especial computer technique has developed to select RSDs for connection in series. At this RSD selection value of leakage current and stability of blocking volt-amps diagram are measured especially. This selection technique is allowed exclude the voltage dividers using for equalization of static voltage for each RSD at assembly. Thus, after such selection switch design can simplify, sizes of switch are increased approximately in 1.5 times, and cost of switch is increased too.This solid state switch has operating voltage of up to 25 kVdc, operating peak current of up to 300 kA at current pulse duration of up to 500 μs. RFNC -VNIIEF plans to use such switch at capacitor bank of laser facility “I skra-6”. This switch is included 15 RSDs with size of 76 mm and blocking voltage of 2.4 kV connected in series and encapsullated into dielectric housing. Very high level of switched power density per volume unit has reached by this switch design. This value is of 2.5 610W/3cm , and this value is exceeded in the several times the same switches based on pulse thyristors.Triggering of all RSDs in switch is provided by the single trigger generator which connected to switch in parallel. Triggering current passes simultaneously through all RSDs connected in series. Such triggering type is allowed to increase efficiency and reliability of triggering circuit for this switch, and this is one more advantage of RSD –switch compared toswitch based on thyristors.For new generation of RSD trigger current has peak value between 1-1.5 kA at pulse duration between 1.5 –2 μs. These values are less in 2-3 times compared to values of trigger current for RSD of the first generation.IV. ConclusionNext generation of reverse-switched dinistors and RSD – switches has been developed Tests of these switches are shown that all –time high level of switched power density per volume unit has reached. The switches are able to work under as mono-pulse and pulse-repeated modes and suitable for many applications of pulsed power.应用于脉冲电源设备的新一代高功率半导体关闭开关1 导言固态半导体开关普遍使用在脉冲功率系统，由于这些开关具有可靠性高，寿命长，使用成本低，同时由于汞与铅的量少能够保证环境的安全。

外文出处：Farhadi, A. (2008). Modeling, simulation, and reduction of conducted electromagnetic interference due to a pwm buck type switching power supply. Harmonics and Quality of Power, 2008. ICHQP 2008. 13th International Conference on, 1 - 6.Modeling, Simulation, and Reduction of Conducted Electromagnetic Interference Due to a PWM Buck Type Switching Power Supply IA. FarhadiAbstract:Undesired generation of radiated or conducted energy in electrical systems is called Electromagnetic Interference (EMI). High speed switching frequency in power electronics converters especially in switching power supplies improves efficiency but leads to EMI. Different kind of conducted interference, EMI regulations and conducted EMI measurement are introduced in this paper. Compliancy with national or international regulation is called Electromagnetic Compatibility (EMC). Power electronic systems producers must regard EMC. Modeling and simulation is the first step of EMC evaluation. EMI simulation results due to a PWM Buck type switching power supply are presented in this paper. To improve EMC, some techniques are introduced and their effectiveness proved by simulation.Index Terms:Conducted, EMC, EMI, LISN, Switching SupplyI. INTRODUCTIONFAST semiconductors make it possible to have high speed and high frequency switching in power electronics []1. High speed switching causes weight and volume reduction of equipment, but some unwanted effects such as radio frequency interference appeared []2. Compliance with electromagnetic compatibility (EMC) regulations is necessary for producers to present their products to the markets. It is important to take EMC aspects already in design phase []3. Modeling and simulation is the most effective tool to analyze EMC consideration before developing the products. A lot of the previous studies concerned the low frequency analysis of power electronics components []4[]5. Different types of power electronics converters are capable to be considered as source of EMI. They could propagate the EMI in both radiated and conducted forms. Line Impedance Stabilization Network (LISN) is required for measurement and calculation of conducted interference level []6. Interference spectrum at the output of LISN is introduced as the EMC evaluation criterion []7[]8. National or international regulations are the references forthe evaluation of equipment in point of view of EMC []7[]8.II. SOURCE, PATH AND VICTIM OF EMIUndesired voltage or current is called interference and their cause is called interference source. In this paper a high-speed switching power supply is the source of interference.Interference propagated by radiation in area around of an interference source or by conduction through common cabling or wiring connections. In this study conducted emission is considered only. Equipment such as computers, receivers, amplifiers, industrial controllers, etc that are exposed to interference corruption are called victims. The common connections of elements, source lines and cabling provide paths for conducted noise or interference. Electromagnetic conducted interference has two components as differential mode and common mode []9.A. Differential mode conducted interferenceThis mode is related to the noise that is imposed between different lines of a test circuit by a noise source. Related current path is shown in Fig. 1 []9. The interference source, path impedances, differential mode current and load impedance are also shown in Fig. 1.B. Common mode conducted interferenceCommon mode noise or interference could appear and impose between the lines, cables or connections and common ground. Any leakage current between load and common ground couldbe modeled by interference voltage source.Fig. 2 demonstrates the common mode interference source, common mode currents Iandcm1 and the related current paths[]9.The power electronics converters perform as noise source Icm2between lines of the supply network. In this study differential mode of conducted interference is particularly important and discussion will be continued considering this mode only.III. ELECTROMAGNETIC COMPATIBILITY REGULATIONS Application of electrical equipment especially static power electronic converters in different equipment is increasing more and more. As mentioned before, power electronics converters are considered as an important source of electromagnetic interference and have corrupting effects on the electric networks []2. High level of pollution resulting from various disturbances reduces the quality of power in electric networks. On the other side some residential, commercial and especially medical consumers are so sensitive to power system disturbances including voltage and frequency variations. The best solution to reduce corruption and improve power quality is complying national or international EMC regulations. CISPR, IEC, FCC and VDE are among the most famous organizations from Europe, USA and Germany who are responsible for determining and publishing the most important EMC regulations. IEC and VDE requirement and limitations on conducted emission are shown in Fig. 3 and Fig. 4 []7[]9.For different groups of consumers different classes of regulations could be complied. Class Afor common consumers and class B with more hard limitations for special consumers are separated in Fig. 3 and Fig. 4. Frequency range of limitation is different for IEC and VDE that are 150 kHz up to 30 MHz and 10 kHz up to 30 MHz respectively. Compliance of regulations is evaluated by comparison of measured or calculated conducted interference level in the mentioned frequency range with the stated requirements in regulations. In united European community compliance of regulation is mandatory and products must have certified label to show covering of requirements []8.IV. ELECTROMAGNETIC CONDUCTED INTERFERENCE MEASUREMENTA. Line Impedance Stabilization Network (LISN)1-Providing a low impedance path to transfer power from source to power electronics converter and load.2-Providing a low impedance path from interference source, here power electronics converter, to measurement port.Variation of LISN impedance versus frequency with the mentioned topology is presented inFig. 7. LISN has stabilized impedance in the range of conducted EMI measurement []7.Variation of level of signal at the output of LISN versus frequency is the spectrum of interference. The electromagnetic compatibility of a system can be evaluated by comparison of its interference spectrum with the standard limitations. The level of signal at the output of LISN in frequency range 10 kHz up to 30 MHz or 150 kHz up to 30 MHz is criterion of compatibility and should be under the standard limitations. In practical situations, the LISN output is connected to a spectrum analyzer and interference measurement is carried out. But for modeling and simulation purposes, the LISN output spectrum is calculated using appropriate software.基于压降型PWM开关电源的建模、仿真和减少传导性电磁干扰摘要：电子设备之中杂乱的辐射或者能量叫做电磁干扰(EMI)。

电子专业词汇的中英文对照电路的基本概念及定律电源source电压源voltage source电流源current source理想电压源ideal voltage source理想电流源ideal current source伏安特性volt-ampere characteristic 电动势electromotive force电压voltage电流current电位potential电位差potential difference欧姆Ohm伏特Volt安培Ampere瓦特Watt焦耳Joule电路circuit电路元件circuit element电阻resistance电阻器resistor电感inductance电感器inductor电容capacitance电容器capacitor电路模型circuit model参考方向reference direction参考电位reference potential欧姆定律Ohm’s law基尔霍夫定律Kirchhoff’s law基尔霍夫电压定律Kirchhoff’s voltage law（KVL）基尔霍夫电流定律Kirchhoff’s current law（KCL）结点node支路branch回路loop网孔mesh支路电流法branch current analysis网孔电流法mesh current analysis结点电位法node voltage analysis电源变换source transformations叠加原理superposition theorem网络network无源二端网络passive two-terminal network有源二端网络active two-terminal network戴维宁定理Thevenin’s theorem诺顿定理Norton’s theorem开路（断路）open circuit短路short circuit开路电压open-circuit voltage短路电流short-circuit current交流电路直流电路direct current circuit (dc)交流电路alternating current circuit (ac)正弦交流电路sinusoidal a-c circuit平均值average value有效值effective value均方根值root-mean-squire value (rms) 瞬时值instantaneous value电抗reactance感抗inductive reactance容抗capacitive reactance法拉Farad亨利Henry阻抗impedance复数阻抗complex impedance相位phase初相位initial phase相位差phase difference相位领先phase lead相位落后phase lag倒相，反相phase inversion频率frequency角频率angular frequency赫兹Hertz相量phasor相量图phasor diagram有功功率active power无功功率reactive power视在功率apparent power功率因数power factor功率因数补偿power-factor compensation串联谐振series resonance并联谐振parallel resonance谐振频率resonance frequency频率特性frequency characteristic幅频特性amplitude-frequency response characteristic相频特性phase-frequency response characteristic截止频率cutoff frequency品质因数quality factor 通频带pass-band带宽bandwidth (BW)滤波器filter一阶滤波器first-order filter二阶滤波器second-order filter低通滤波器low-pass filter高通滤波器high-pass filter带通滤波器band-pass filter带阻滤波器band-stop filter转移函数transfer function波特图Bode diagram傅立叶级数Fourier series三相电路三相电路three-phase circuit三相电源three-phase source对称三相电源symmetrical three-phase source对称三相负载symmetrical three-phase load相电压phase voltage相电流phase current线电压line voltage线电流line current三相三线制three-phase three-wire system三相四线制three-phase four-wire system三相功率three-phase power星形连接star connection(Y-connection) 三角形连接triangular connection(D- connection ,delta connection)中线neutral line电路的暂态过程分析暂态transient state稳态steady state暂态过程，暂态响应transient response 换路定理low of switch一阶电路first-order circuit三要素法three-factor method时间常数time constant积分电路integrating circuit微分电路differentiating circuit磁路与变压器磁场magnetic field磁通flux磁路magnetic circuit磁感应强度flux density磁通势magnetomotive force磁阻reluctance电动机直流电动机dc motor交流电动机ac motor异步电动机asynchronous motor同步电动机synchronous motor三相异步电动机three-phase asynchronous motor单相异步电动机single-phase asynchronous motor旋转磁场rotating magnetic field定子stator转子rotor转差率slip起动电流starting current起动转矩starting torque额定电压rated voltage 额定电流rated current额定功率rated power机械特性mechanical characteristic继电器-接触器控制按钮button熔断器fuse开关switch行程开关travel switch继电器relay接触器contactor常开(动合)触点normally open contact 常闭(动断)触点normally closed contact 时间继电器time relay热继电器thermal overload relay中间继电器intermediate relay可编程控制器（PLC）可编程控制器programmable logic controller语句表statement list梯形图ladder diagram半导体器件本征半导体intrinsic semiconductor掺杂半导体doped semiconductorP型半导体P-type semiconductorN型半导体N--type semiconductor自由电子free electron空穴hole载流子carriersPN结PN junction扩散diffusion漂移drift二极管diode硅二极管silicon diode锗二极管germanium diode阳极anode阴极cathode发光二极管light-emitting diode (LED) 光电二极管photodiode稳压二极管Zener diode晶体管（三极管）transistorPNP型晶体管PNP transistorNPN型晶体管NPN transistor发射极emitter集电极collector基极base电流放大系数current amplification coefficient场效应管field-effect transistor (FET) P沟道p-channelN沟道n-channel结型场效应管junction FET（JFET）金属氧化物半导体metal-oxide semiconductor (MOS)耗尽型MOS场效应管depletion mode MOSFET（D-MOSFET）增强型MOS场效应管enhancement mode MOSFET（E-MOSFET）源极source栅极grid漏极drain跨导transconductance夹断电压pinch-off voltage热敏电阻thermistor开路open短路shorted 基本放大器放大器amplifier正向偏置forward bias反向偏置backward bias静态工作点quiescent point (Q-point)等效电路equivalent circuit电压放大倍数voltage gain总的电压放大倍数overall voltage gain 饱和saturation截止cut-off放大区amplifier region饱和区saturation region截止区cut-off region失真distortion饱和失真saturation distortion截止失真cut-off distortion零点漂移zero drift正反馈positive feedback负反馈negative feedback串联负反馈series negative feedback并联负反馈parallel negative feedback 共射极放大器common-emitter amplifier 射极跟随器emitter-follower共源极放大器common-source amplifier 共漏极放大器common-drain amplifier 多级放大器multistage amplifier阻容耦合放大器resistance-capacitance coupled amplifier直接耦合放大器direct- coupled amplifier输入电阻input resistance输出电阻output resistance负载电阻load resistance动态电阻dynamic resistance负载电流load current旁路电容bypass capacitor耦合电容coupled capacitor直流通路direct current path交流通路alternating current path直流分量direct current component交流分量alternating current component 变阻器（电位器）rheostat电阻（器）resistor电阻（值）resistance电容（器）capacitor电容（量）capacitance电感（器，线圈）inductor电感（量），感应系数inductance正弦电压sinusoidal voltage集成运算放大器及应用差动放大器differential amplifier运算放大器operationalamplifier(op-amp)失调电压offset voltage失调电流offset current共模信号common-mode signal差模信号different-mode signal共模抑制比common-mode rejection ratio (CMRR)积分电路integrator（circuit）微分电路differentiator（circuit）有源滤波器active filter低通滤波器low-pass filter高通滤波器high-pass filter带通滤波器band-pass filter带阻滤波器band-stop filter 波特沃斯滤波器Butterworth filter切比雪夫滤波器Chebyshev filter贝塞尔滤波器Bessel filter截止频率cut-off frequency上限截止频率upper cut-off frequency下限截止频率lower cut-off frequency中心频率center frequency带宽Bandwidth开环增益open-loop gain闭环增益closed-loop gain共模增益common-mode gain输入阻抗input impedance电压跟随器voltage-follower电压源voltage source电流源current source单位增益带宽unity-gain bandwidth频率响应frequency response频响特性（曲线）response characteristic 波特图the Bode plot稳定性stability补偿compensation比较器comparator迟滞比较器hysteresis comparator阶跃输入电压step input voltage仪表放大器instrumentation amplifier隔离放大器isolation amplifier对数放大器log amplifier反对数放大器antilog amplifier反馈通道feedback path反向漏电流reverse leakage current相位phase相移phase shift锁相环phase-locked loop(PLL)锁相环相位监测器PLL phase detector 和频sum frequency差频difference frequency波形发生电路振荡器oscillatorRC振荡器RC oscillatorLC振荡器LC oscillator正弦波振荡器sinusoidal oscillator三角波发生器triangular wave generator 方波发生器square wave generator幅度magnitude电平level饱和输出电平（电压）saturated output level功率放大器功率放大器power amplifier交越失真cross-over distortion甲类功率放大器class A power amplifier 乙类推挽功率放大器class B push-pull power amplifierOTL功率放大器output transformerless power amplifierOCL功率放大器output capacitorless power amplifier直流稳压电源半波整流full-wave rectifier全波整流half-wave rectifier电感滤波器inductor filter电容滤波器capacitor filter串联型稳压电源series (voltage) regulator开关型稳压电源switching (voltage) regulator集成稳压器IC (voltage) regulator 晶闸管及可控整流电路晶闸管thyristor单结晶体管unijunction transistor（UJT）可控整流controlled rectifier可控硅silicon-controlled rectifier峰点peak point谷点valley point控制角controlling angle导通角turn-on angle门电路与逻辑代数二进制binary二进制数binary number十进制decimal十六进制hexadecimal二-十进制binary coded decimal （BCD）门电路gate三态门tri-state gate与门AND gate或门OR gate非门NOT gate与非门NAND gate或非门NOR gate异或门exclusive-OR gate反相器inverter布尔代数Boolean algebra真值表truth table卡诺图the Karnaugh map逻辑函数logic function逻辑表达式logic expression组合逻辑电路组合逻辑电路combination logic circuit 译码器decoder编码器coder比较器comparator半加器half-adder全加器full-adder七段显示器seven-segment display 时序逻辑电路时序逻辑电路sequential logic circuit R-S 触发器R-S flip-flopD触发器D flip-flopJ-K触发器J-K flip-flop主从型触发器master-slave flip-flop 置位set复位reset直接置位端direct-set terminal直接复位端direct-reset terminal寄存器register移位寄存器shift register双向移位寄存器bidirectional shift register计数器counter同步计数器synchronous counter异步计数器asynchronous counter 加法计数器adding counter减法计数器subtracting counter定时器timer清除（清0）clear载入load时钟脉冲clock pulse触发脉冲trigger pulse上升沿positive edge下降沿negative edge 时序图timing diagram波形图waveform脉冲波形的产生与整形单稳态触发器monostable flip-flop双稳态触发器bistable flip-flop无稳态振荡器astable oscillator晶体crystal555定时器555 timer模拟信号与数字信号的相互转换模拟信号analog signal数字信号digital signalAD转换器analog -digital converter (ADC) DA转换器digital-analog converter (DAC)半导体存储器只读存储器read-only memory（ROM）随机存取存储器random-access memory（RAM）可编程ROM programmable ROM （PROM）Linear Control System(线性系统), Single Input Single Output(单输入单输出), Laplace Transform(拉普拉斯变换), Differential Equations(微分方程), Transfer Functions(传递函数), Models of System(系统模型), Block Diagrams(方框图), Mason’s Gain Formula(梅森公式), First-order System(一阶系统), Second-order System(二阶系统), Higher-order System(高阶系统), Close-loop Control System(闭环控制系统), Stability(稳定性), Transient Response(瞬态响应), Routh-Hurwitz Stability Criterion(劳斯判据), Steady-state Accuracy(稳态精度), Root-locus(根轨迹), Root-locus Principles(根轨迹基本规则), Frequency Responses(频率响应), Bode Diagrams(波特图), Nyquist Criterion(奈氏判据), Relative Stability(相对稳定性).。

Electric Power SystemElectrical power system refers to remove power and electric parts of the part,It includes substation, power station and distribution. The role of the power grid is connected power plants and users and with the minimum transmission and distribution network disturbance through transport power, with the highest efficiency and possibility will voltage and frequency of the power transmission to the user fixed .Grid can be divided into several levels based on the operating voltage transmission system, substructure, transmission system and distribution system, the highest level of voltage transmission system is ZhuWangJia or considered the high power grids. From the two aspects of function and operation, power can be roughly divided into two parts, the transmission system and substation. The farthest from the maximum output power and the power of the highest voltage grade usually through line to load. Secondary transmission usually refers to the transmission and distribution system is that part of the middle. If a plant is located in or near the load, it might have no power. It will be direct access to secondary transmission and distribution system. Secondary transmission system voltage grade transmission and distribution system between voltage level. Some systems only single second transmission voltage, but usually more than one. Distribution system is part of the power system and its retail service to users, commercial users and residents of some small industrial users. It is to maintain and in the correct voltage power to users responsible. In most of the system, Distribution system accounts for 35% of the total investment system President to 45%, and total loss of system of the half .More than 220kv voltage are usually referred to as Ultra high pressure, over 800kv called high pressure, ultra high voltage and high pressure have important advantages, For example, each route high capacity, reduce the power needed for the number of transmission. In as high voltage to transmission in order to save a conductor material seem desirable, however, must be aware that high voltage transmission can lead to transformer, switch equipment and other instruments of spending increases, so, for the voltage transmission to have certain restriction, allows it to specific circumstances in economic use. Although at present, power transmission most is through the exchange of HVDC transmission, and the growing interest in, mercury arc rectifier and brake flow pipe into the ac power generation and distribution that change for the high voltage dc transmission possible.Compared with the high-voltage dc high-voltage ac transmission has the following some advantages: (1) the communication with high energy; (2) substation of simple maintenance and communication cost is low; (3) ac voltage can easily and effectively raise or lower, it makes the power transmission and high pressure With safety voltage distributionHVDC transmission and high-voltage ac transmission has the following advantages: (1) it only need two phase conductors and ac transmission to three-phase conductors; (2) in the dc transmission impedance, no RongKang, phase shift and impact overvoltage; (3) due to the same load impedance, no dc voltage, and transfer of the transmission line voltage drop less communication lines, and for this reason dc transmission line voltage regulator has better properties; (4) in dc system without skin effect. Therefore, the entire section of route conductors are using; (5) for the same work, dc voltage potential stress than insulation. Therefore dc Wire need less insulation; (6) dc transmission line loss, corona to little interference lines of communication; (7) HVDC transmission without loss of dielectric, especially in cable transmission; (8) in dc system without stability and synchronization of trouble.A transmission and the second transmission lines terminated in substation or distribution substations, the substation and distribution substations, the equipment including power and instrument transformer and lightning arrester, with circuit breaker, isolating switch, capacitor set, bus and a substation control equipment, with relays for the control room of the equipment. Some of the equipment may include more transformer substations and some less, depending on their role in the operation. Some of the substation is manual and other is automatic. Power distribution system through the distribution substations. Some of them by many large capacity transformer feeders, large area to other minor power transformer capacity, only a near load control, sometimes only a doubly-fed wire feeders (single single variable substation)Now for economic concerns, three-phase three-wire type communication network is widely used, however, the power distribution, four lines using three-phase ac networks.Coal-fired power means of main power generating drive generators, if coal energy is used to produce is pushing the impeller, then generate steam force is called the fire. Use coal produces steam to promote the rotating impeller machine plant called coal-fired power plants. In the combustion process, the energy stored in the coal to heat released,then the energy can be transformed into the form within vapor. Steam into the impeller machine work transformed into electrical energy.Coal-fired power plants could fuel coal, oil and natural gas is. In coal-fired power plant, coal and coal into small pieces first through the break fast, and then put out. The coal conveyer from coal unloader point to crush, then break from coal, coal room to pile and thence to power. In most installations, according to the needs of coal is, Smash the coal storage place, no coal is through the adjustable coal to supply coal, the broken pieces of coal is according to the load changes to control needs. Through the broken into the chamber, the coal dust was in the second wind need enough air to ensure coal burning.In function, impeller machine is used to high temperature and high pressure steam energy into kinetic energy through the rotation, spin and convert electricity generator. Steam through and through a series of impeller machine parts, each of which consists of a set of stable blade, called the pipe mouth parts, even in the rotor blades of mobile Li called. In the mouth parts (channel by tube nozzle, the steam is accelerating formation) to high speed, and the fight in Li kinetic energy is transformed into the shaft. In fact, most of the steam generator is used for air is, there is spread into depression, steam turbine of low-pressure steam from the coagulation turbine, steam into the condenses into water, and finally the condensate water is to implement and circulation.In order to continuous cycle, these must be uninterrupted supply: (1) fuel; (2) the air (oxygen) to the fuel gas burning in the configuration is a must; (3) and condenser, condensed from the condensed water supply, sea and river to lake. Common cooling tower; (4) since water vapour in some places in circulation, will damage process of plenty Clean the supply.The steam power plant auxiliary system is running. For a thermal power plant, the main auxiliary system including water system, burning gas and exhaust systems, condensation system and fuel system. The main auxiliary system running in the water pump, condensation and booster pump, coal-fired power plants in the mill equipment. Other power plant auxiliary equipment including air compressors, water and cooling water system, lighting and heating systems, coal processing system. Auxiliary equipment operation is driven by motor, use some big output by mechanical drive pump and some of the impeller blades, machine drive out from the main use of water vaporimpeller machine. In coal-fired power plant auxiliary equipment, water supply pump and induced draft fan is the biggest need horsepower.Most of the auxiliary power generating unit volume increased significantly in recent years, the reason is required to reduce environment pollution equipment. Air quality control equipment, such as electrostatic precipitator, dust collection of flue gas desulfurization, often used in dust in the new coal-fired power plants, and in many already built in power plant, the natural drive or mechanical drive, fountain, cooling tower in a lake or cooling canal has been applied in coal-fired power plants and plants, where the heat release need to assist cooling system.In coal-fired power stations, some device is used to increase the thermal energy, they are (1) economizer and air preheater, they can reduce the heat loss; (2) water heater, he can increase the temperature of water into boiling water heaters; (3) they can increase and filter the thermal impeller.Coal-fired power plants usually requires a lot of coal and coal reservoirs, however the fuel system in power plant fuel handling equipment is very simple, and almost no fuel oil plants.The gas turbine power plants use gas turbine, where work is burning gas fluid. Although the gas turbine must burn more expensive oil or gas, but their low cost and time is short, and can quickly start, they are very applicable load power plant. The gas turbine burn gas can achieve 538 degrees Celsius in the condensing turbine, however, the temperature is lower, if gas turbine and condenser machine, can produce high thermal efficiency. In gas turbine turbine a combined cycle power plant. The gas through a gas turbine, steam generator heat recovery in there were used to generate vapor heat consumption. Water vapor and then through a heated turbine. Usually a steam turbine, and one to four gas turbine power plant, it must be rated output power.。

DC Switching Power Supply Protection TechnologyAbstract: The DC switching power supply protection system, protection system design principles and machine protection measures, an analysis of switching power supply in the range of protected characteristics and its design methodology, introduced a number of practical protection circuit.Keywords: switching power supply protection circuit system designA、IntroductionDC switching regulator used in the price of more expensive high-power switching devices, the control circuit is also more complex, In addition, the load switching regulators are generally used a large number of highly integrated electronic systems installed devices. Transistors and integrated device tolerance electricity, less heat shocks. Switching Regulators therefore should take into account the protection of voltage regulators and load their own safety. Many different types of circuit protection, polarity protection, introduced here, the program protection, over-current protection, over-voltage protection, under-voltage protection and over-temperature protection circuit. Usually chosen to be some combination of protection, constitutes a complete protection system.B、Polarity protectionDC switching regulator input is generally not regulated DC power supply. Operating errors or accidents as a result of the situation will take its wrong polarity; switching power supply will be damaged. Polarity protection purposes, is to make the switching regulator only when the correct polarity is not connected to DC power supply regulator to work at. Connecting a single device can achieve power polarity protection. Since the diode D to flow through switching regulator input total current, this circuit applied in a low-power switching regulator more suitable. Power in the larger occasion,while the polarity protection circuit as a procedure to protect a link, save the power required for polarity protection diodes, power consumption will be reduced. In order to easy to operate, make it easier to identify the correct polarity or not, collect the next light.C、Procedures to protectSwitching power supply circuit is rather complicated, basically can be divided into low-power and high-power part of the control part of the switch. Switch is a high-power transistors, for the protection of the transistor switch is turned on or off power safety, we must first modulator, amplifier and other low-power control circuit. To this end, the boot to ensure the correct procedures. Switching Regulators generally take the input of a small inductor, the input filter capacitor. Moment in the boot, filter capacitor will flow a lot of surge current, the surge current can be several times more than the normal input current. Such a large surge current may contact the general power switch or relay contact melting, and the input fuse. In addition, the capacitor surge current will damage to shorten the life span of premature damage. To this end, the boot should be access to a current limiting resistor, through the current limiting resistor to capacitor charging. In order not to make the current limiting resistor excessive power consumption, thus affecting the normal switching regulator, and the transient process in the boot after a short period then automatically relays it to DC power supply directly to the switching regulator power supply. This circuit switching regulator called a "soft start" circuit.Switching regulator control circuit of the logic components required or op-amp auxiliary power supply. To this end, the auxiliary power supply must be in the switch circuit. This control circuit can be used to ensure the boot. Normal boot process is: to identify the polarity of input power, voltage protection procedures → boot → auxiliary power supply circuit and through current limiting resis tor R of the switching regulator input capacitor C →charge modulation switching regulator circuit, → short-circuit current limiting resistor stability switching regulator.In the switching regulator, the machines just because the output capacitance, and charge to the rated output voltage value of the need for a certain period of time. During this time, sampling the output amplifier with low input voltage sampling, closed-loop regulation characteristics of the system will force the switching of the transistor conduction time lengthened, so that switching transistor during this period will tend to continuous conduction, and easily damaged. To this end, the requirements of this paragraph in the boot time, the switch to switch the output modulation circuit transistor base drive signal of the pulse width modulation, can guarantee the switching transistor by the cut-off switches are becoming more and more normal state, therefore the protection of the setting up of a boot to tie in with the soft start.D、Over-current protectionWhen the load short-circuit, overload control circuit failure or unforeseen circumstances, such as would cause the flow of switching voltage regulator transistor current is too large, so that increased power tubes, fever, if there is no over-current protection device, high power switching transistor may be damaged. Therefore, the switching regulator in the over-current protection is commonly used. The most economical way is to use simple fuse. As a result of the heat capacity of small transistors, general fuse protection in general can not play a role in the rapid fuse common fuse. This method has the advantage of the protection of vulnerable, but it needs to switch transistor in accordance with specific security requirements of the work area to select the fuse specifications. This disadvantage is over-current protection measures brought about by the inconvenience of frequent replacement of fuses.Linear voltage regulator commonly used in the protection and currentlimiting to protect the cut-off in the switching regulator can be applied. However, according to the characteristics of switching regulators, the protection circuit can not directly control the output transistor switches, and over current protection must be converted to pulse output commands to control the modulator to protect the transistor switch. In order to achieve over-current protection are generally required sampling resistor in series in the circuit, this will affect the efficiency of power supply, so more for low-power switching regulator of occasions. In the high-power switching power supply, by taking into account the power consumption should be avoided as far as possible access to the sampling resistor. Therefore, there will usually be converted to over-current protection, and under-voltage protection.E、Over-voltage protectionSwitching regulator's input over-voltage protection, including over-voltage protection and output over-voltage protection. Switching regulator is not used in DC power supply voltage regulator and rectifier, such as battery voltage, if too high, so switching regulator is not working properly, or even damage to internal devices, therefore, it is necessary to use the input over-voltage protection circuit. Using transistors and relays protection circuit.In the circuit, when the input DC power supply voltage higher than the voltage regulator diode breakdown voltage value, the breakdown voltage regulator tube, a current flowing through resistor R, so that V turn-on transistor, relay, normally closed contact off open, cut off the input. Voltage regulator voltage regulator which controls the value of Vs. = Earwax-UBE. The polarity of input power with the input protection circuit can be combined with over-voltage protection, polarity protection constitute a differential circuit and over voltage protection.Output over-voltage protection switching power supply is essential. In particular, for the 5V output of the switching regulator, it is a lot of load on a high level of integration of the logic device. If at work, switching regulator sudden damage to the switch transistor, the output potential may be increased immediately to the importation of non-regulated DC power supply voltage value, causing great loss instantaneous. Commonly used method is short-circuit protection thirsted. The simplest over-voltage protection circuit. When the output voltage is too high, the regulator tube breakdown triggered thirstier turn-on, the output short-circuit, resulting in over-current through the fuse or circuit protective device to cut off the input to protect the load. This circuit is equivalent to the response time of the opening time of thirstier is about 5 ~ 10μs. The disadvantage is that its action is fixed voltage, temperature coefficient, and action points of instability. In addition, there is a voltage regulator control parameters of the discrete, model over-voltage start-up the same but has different values, difficult to debug. Esc a sudden increase in output voltage, transistors V1, V2 conduction, the thruster conduction. Reference voltage Vs. by type.F、Under-voltage protectionOutput voltage below the value to reflect the input DC power supply, switching regulator output load internal or unusual occurrence. Input DC power supply voltage drops below the specified value would result in switching regulator output voltage drops, the input current increases, not only endanger the switching transistor, but also endanger the input power. Therefore, in order to set up due to voltage protection. Due to simple voltage protection.When no voltage regulator input normal, ZD breakdown voltage regulator tube, transistors V conduction, the relay action, contact pull-in, power-switching regulator. When the input below the minimum allowable voltage value, the regulator tube ZD barrier, V cut-off, contact Kai-hop,switching regulator can not work. Internal switching regulator, as the control switch transistor circuit disorders or failure will decrease the output voltage; load short-circuit output voltage will also decline.Especially in the reversed-phase step-up or step-up switching regulator DC voltage of the protection due to over-current protection with closely related and therefore more important. Implementation of Switching Regulators in the termination of the output voltage comparators.Normally, there is no comparator output, once the voltage drops below the allowable value in the comparator on the flip, drive alarm circuit; also fed back to the switching regulator control circuit, so that switching transistor cut-off or cut off the input power.G、Over-temperature protectionSwitching regulator and the high level of integration of light-weight small volume, with its unit volume greatly increased the power density, power supply components to its work within the requirements of the ambient temperature is also a corresponding increase. Otherwise, the circuit performance will deteriorate premature component failure. Therefore, in high-power switching regulator should be set up over-temperature protection.Relays used to detect the temperature inside the power supply temperature, when the internally generated power supply overheating, the temperature of the relay on the action, so that whole circuit in a warning alarm, and the realization of the power supply over-temperature protection. Temperature relay can be placed in the vicinity of the switching transistor, the general high-power tube shell to allow the maximum temperature is 75 ℃, adjust the temperature setting to 60 ℃. When the shell after the temperature exceeds the allowable value to cut off electrical relay on the switch protection. Semiconductor switching device thermal "hot thirstier," in the over-temperature protection, played an important role. It can be used asdirected circuit temperature. Under the control of p-hot-gate thirstier (TT102) characteristics, by RT value to determine the temperature of the device turn-on, RT greater the temperature the lower the turn-on. When placed near the power switching transistor or power device, it will be able to play the role of temperature instructions. When the power control the temperature of the shell or the internal device temperature exceeds the allowed value, the heat conduction thirstier on, so that LED warning light. If the opt coupler with, would enable the whole circuit alarm action to protect the switching regulator. It can also be used as a power transistor as the over-temperature protection, crystal switch the base current by n-type gate control thirstier TT201 thermal bypass, cut-off switch to cut off the collector current to prevent overheating.I、ConclusionDiscussed above in the switching regulator of a variety of conservation, and introduces a number of specific ways to achieve. Of a given switching power supply is concerned, but also protection from the whole to consider the following points:1) The switching regulator used in the switching transistor in the DC security restrictions on the work of regional work. The transistor switches selected by the manual available transistors get DC safe working area. According to the maximum collector current to determine the input value of over-current protection. However, the instantaneous maximum value should be converted to the average current. At rated output current and output voltage conditions, the switch of the dynamic load line does not exceed a safe working area DC maximum input voltage, input over-voltage protection is the voltage value.2)The switching regulator output limit given by the technical indicators within. Work within the required temperature range, the switching regulator's output voltage, the lower limit of the output is off, due to thevoltage value of voltage protection. Over-current protection can be based on the maximum output current to determine. False alarm in order not to protect the value of a certain margin to remain appropriate.3)From the above two methods to determine the protection after the power supply device in accordance with the needs of measures to determine the alarm. Measures the general alarm sound and light alarm two police. Voice of the police applied to more complex machines, power supply parts and do not stand out in a place, it can give staff an effective warning of failure; optical Police instructions can be eye-catching and fault alarm and pointed out that the fault location and type. Protection measures should be protected as to determine the location. In the high-power, multi-channel power supply, always paying, DC circuit breakers, relays, etc. high-sensitivity auto-protection measures, to cut off the input power supply to stop working the system from damage. Through the logic control circuit to make the appropriate program cut-off switch transistor is sensitive it is convenient and economic. This eliminated large, long response time, the price of your high-power relay or circuit breaker.4) The power of putting in the protection circuit will be affected after the reliability of the system, for which want to protect the reliability of the circuit itself is higher in order to improve the reliability of the entire power system, thereby increasing its own power supply MTBF. This requires the protection of strict logic, the circuit is simple, at least components, In addition to the protection circuit should also be considered a failure of maintenance of their difficulty and their power to protect the damage.Therefore, we must be comprehensive and systematic consideration of a variety of switching power supply protection measures to ensure the normal operation of switching power supplies and high-efficiency and high reliability.直流开关稳压电源的保护技术摘要：讨论了直流开关稳压电源的保护系统,提出保护系统设计的原则和整机保护的措施，分析了开关稳压电源中的各种保护的特点及其设计方法,介绍了几种实用保护电路。

中英文对照外文翻译文献(文档含英文原文和中文翻译)DC Switching Power Supply Protection TechnologyAbstract: The DC switching power supply protection system, protection s ystem design principles and machine protection measures, an analysis of switching power supply in the range of protected characteristics and its d esign methodology, introduced a number of practical protection circuit. Keywords: switching power supply protection circuit system design A、Introduction.DC switching regulator used in the price of more expensive high-powerswitching devices, the control circuit is also more complex, In addition, th e load switching regulators are generally used a large number of highly in tegrated electronic systems installed devices. Transistors and integrated device tolerance electricity, less heat shocks. Switching Regulators theref ore should take into account the protection of voltage regulators and loa d their own safety. Many different types of circuit protection, polarity pro tection, introduced here, the program protection, over-current protectio n, over-voltage protection, under-voltage protection and over-temperatu re protection circuit. Usually chosen to be some combination of protectio n, constitutes a complete protection system.B、Polarity protectionDC switching regulator input is generally not regulated DC power supply. Operating errors or accidents as a result of the situation will take its wron g polarity; switching power supply will be damaged. Polarity protection p urposes, is to make the switching regulator only when the correct polarit y is not connected to DC power supply regulator to work at. Connecting a single device can achieve power polarity protection. Since the diode D t o flow through switching regulator input total current, this circuit applied in a low-power switching regulator more suitable. Power in the larger oc casion, while the polarity protection circuit as a procedure to protect a li nk, save the power required for polarity protection diodes, power consumption will be reduced. In order to easy to operate, make it easier to ide ntify the correct polarity or not, collect the next light.C、Procedures to protectSwitching power supply circuit is rather complicated, basically can be divi ded into low-power and high-power part of the control part of the switch . Switch is a high-power transistors, for the protection of the transistor s witch is turned on or off power safety, we must first modulator, amplifier and other low-power control circuit. To this end, the boot to ensure the correct procedures. Switching Regulators generally take the input of a sm all inductor, the input filter capacitor. Moment in the boot, filter capacito r will flow a lot of surge current, the surge current can be several times m ore than the normal input current. Such a large surge current may contac t the general power switch or relay contact melting, and the input fuse. I n addition, the capacitor surge current will damage to shorten the life sp an of premature damage. To this end, the boot should be access to a curr ent limiting resistor, through the current limiting resistor to capacitor cha rging. In order not to make the current limiting resistor excessive power c onsumption, thus affecting the normal switching regulator, and the transi ent process in the boot after a short period then automatically relays it t o DC power supply directly to the switching regulator power supply. This circuit switching regulator called a "soft start" circuit. Switching regulator control circuit of the logic components required or op-amp auxiliary p ower supply. To this end, the auxiliary power supply must be in the switc h circuit. This control circuit can be used to ensure the boot. Normal boo t process is: to identify the polarity of input power, voltage protection pr ocedures → boot → auxiliary power supply circuit and through current li miting resistor R of the switching regulator input capacitor C →charge modulation switching regulator circuit, → short-circuit current limiting re sistor stability switching regulator. In the switching regulator, the machi nes just because the output capacitance, and charge to the rated output voltage value of the need for a certain period of time. During this time, s ampling the output amplifier with low input voltage sampling, closed-loo p regulation characteristics of the system will force the switching of the t ransistor conduction time lengthened, so that switching transistor during this period will tend to continuous conduction, and easily damaged. To t his end, the requirements of this paragraph in the boot time, the switch t o switch the output modulation circuit transistor base drive signal of the pulse width modulation, can guarantee the switching transistor by the cu t-off switches are becoming more and more normal state, therefore the protection of the setting up of a boot to tie in with the soft start.D、Over-current protectionWhen the load short-circuit, overload control circuit failure or unforesee n circumstances, such as would cause the flow of switching voltage regulator transistor current is too large, so that increased power tubes, fever, i f there is no over-current protection device, high power switching transis tor may be damaged. Therefore, the switching regulator in the over-curr ent protection is commonly used. The most economical way is to use sim ple fuse. As a result of the heat capacity of small transistors, general fuse protection in general can not play a role in the rapid fuse common fuse. This method has the advantage of the protection of vulnerable, but it ne eds to switch transistor in accordance with specific security requirements of the work area to select the fuse specifications. This disadvantage is ov er-current protection measures brought about by the inconvenience of fr equent replacement of fuses. Linear voltage regulator commonly used i n the protection and current limiting to protect the cut-off in the switchi ng regulator can be applied. However, according to the characteristics of switching regulators, the protection circuit can not directly control the ou tput transistor switches, and over current protection must be converted t o pulse output commands to control the modulator to protect the transis tor switch. In order to achieve over-current protection are generally requ ired sampling resistor in series in the circuit, this will affect the efficiency of power supply, so more for low-power switching regulator of occasions. In the high-power switching power supply, by taking into account the po wer consumption should be avoided as far as possible access to the sam pling resistor. Therefore, there will usually be converted to over-current protection, and under-voltage protection.F、Under-voltage protectionOutput voltage below the value to reflect the input DC power supply, swi tching regulator output load internal or unusual occurrence. Input DC po wer supply voltage drops below the specified value would result in switc hing regulator output voltage drops, the input current increases, not only endanger the switching transistor, but also endanger the input power. T herefore, in order to set up due to voltage protection. Due to simple volt age protection. When no voltage regulator input normal, ZD breakdow n voltage regulator tube, transistors V conduction, the relay action, conta ct pull-in, power-switching regulator. When the input below the minimu m allowable voltage value, the regulator tube ZD barrier, V cut-off, conta ct Kai-hop, switching regulator can not work. Internal switching regula tor, as the control switch transistor circuit disorders or failure will decrea se the output voltage; load short-circuit output voltage will also decline.Especially in the reversed-phase step-up or step-up switching regulator D C voltage of the protection due to over-current protection with closely re lated and therefore more important. Implementation of Switching Regula tors in the termination of the output voltage comparators. Normally, th ere is no comparator output, once the voltage drops below the allowable value in the comparator on the flip, drive alarm circuit; also fed back to the switching regulator control circuit, so that switching transistor cut-off or cut off the input power.G、Over-temperature protectionSwitching regulator and the high level of integration of light-weight small volume, with its unit volume greatly increased the power density, power supply components to its work within the requirements of the ambient t emperature is also a corresponding increase. Otherwise, the circuit perfo rmance will deteriorate premature component failure. Therefore, in high -power switching regulator should be set up over-temperature protectio n. Relays used to detect the temperature inside the power supply temp erature, when the internally generated power supply overheating, the te mperature of the relay on the action, so that whole circuit in a warning al arm, and the realization of the power supply over-temperature protectio n. Temperature relay can be placed in the vicinity of the switching transis tor, the general high-power tube shell to allow the maximum temperatur e is 75 ℃, adjust the temperature setting to 60 ℃. When the shell after t he temperature exceeds the allowable value to cut off electrical relay on the switch protection. Semiconductor switching device thermal "hot thirs tier," in the over-temperature protection, played an important role. It can be used as directed circuit temperature. Under the control of p-ho t-gate thirstier (TT102) characteristics, by RT value to determine the tem perature of the device turn-on, RT greater the temperature the lower theturn-on. When placed near the power switching transistor or power devi ce, it will be able to play the role of temperature instructions. When the power control the temperature of the shell or the internal device temper ature exceeds the allowed value, the heat conduction thirstier on, so that LED warning light. If the opt coupler with, would enable the whole circui t alarm action to protect the switching regulator. It can also be used as a power transistor as the over-temperature protection, crystal switch the b ase current by n-type gate control thirstier TT201 thermal bypass, cut-off switch to cut off the collector current to prevent overheating.H、 The future development of relay protectionProtection technology to future trends is computerized, network, intellig ent, protection and control, measurement and data communications inte gration development.1) ComputerizedAlong with the rapid development of computer hardware, microcompute r protection and development in hardware. Former north electricity insti tute of computer line protection hardware has experienced three develo pment stages: from eight single CPU structure of the microcomputer rela y protection, less than 5 years time to develop more CPU structure, and t o develop the large don't bus module, performance greatly improve mod ule structure, widely used. Huazhong university of science and technolog y development of microcomputer protection from 8 bits CPU, is the corepart in polymerizing-kettle development based on 32-bit microcomputer protection. Nanjing institute of electrical automation began a 16-bit CP U is developed on the basis of computer line protection, has been wides pread in the study, also protect the hardware system 32 bits. The devel opment of southeast university computer hardware and equipment to pr otect and improve through a lot. Tianjin university is a start with more th an 16 bits CPU developed on the basis of computer line protection, whic h began in 1988 study 32-bit digital signal processor (DSP) for the protect ion and control, measuring devices, microcomputer integrated with Zhuh ai jin electrical automation equipment company developed into a fully fu nctional 32-bit big modules, a module is a small computer. Using 32-bit microcomputer chip is not only because the accuracy and precision of th e A/D converter by the resolution limit, more than 16 when converting s peed and cost is unacceptable, More important is the 32-bit microcompu ter chip with high integrity, high frequency and computing speed and lar ge space, rich addressing the command system and more input output. T he CPU registers, data bus, the address bus are 32-bit memory managem ent function, and memory protection function and tasks, and the convers ion function will Cache (Cache) and floating-point components are integr ated in the CPU.2）NetworkPower system of microcomputer protection requirement, besides improving the basic function of protection, also should have the capacity of the fault information and data storage space, long-term fast data processing function, strong communication ability, and other protection and control devices and the whole system by sharing network dispatching data, infor mation and network resources, the ability to program in a high-level lang uage, etc. This requires microcomputer protection device is equivalent to a PC. In the early development of computer to protect, once thought to use a small computer finish relay protection device. Due to the large size, then minicomputers high cost and reliability of this idea is not reality. No w, with microprocessor-based protection function of similar size, speed, work-managing machine greatly exceed the storage capacity of 9 minicomputer, therefore, make use of the relay protection sets polymeriz ing-kettle time is ripe, this is the development direction of the microcom puter relay protection. Tianjin University has developed with microproc essor-based protection device with an identical structure reform polymer izing-kettle of relay protection device. This device has several advantages : (1) 486PC machine can meet all the functions of the current and future demands of microcomputer protection function. (2) dimension and struc ture and the current protection device, exquisite workmanship, shockpro of, prevent overheating, preventing electromagnetic interference ability i s strong, can run in very bad working environment, cost can be accepted.(3) using STD bus or PC bus, hardware modular, for different protection can be arbitrarily choose different modules, flexible configuration, easy ex tension. The microcomputer relay protection device, computerized is irr eversible trend. But how to better satisfy power system, how to further i mprove the reliability of the relay protection, and how to obtain more ec onomic benefit and social benefit, still must specifically in-depth researc h. 820 networks The computer network information and data communi cation tool has become the mainstay of the information age, make huma n production technology and social life of the fundamental changes have taken place. It is deeply affect all industries, as well as various industry pr ovides powerful means of communication. So far, in addition to the differ ential protection disoperation and protection of the relay protection devi ce, all can only protect the electricity installation reaction. Protection fun ction is limited, reduce accidents resection fault components. This is mai nly due to the lack of data communications. Strong Foreign had put forw ard the concept of protection system, which was mainly refers to the safe ty automatic device. Because of the relay protection function not only fa ult components and limit resection impact accident (this is to ensure p riority), the safe and stable operation of the whole system. This requires each protection unit can be altogetherI、ConclusionDiscussed above in the switching regulator of a variety of conservation, a nd introduces a number of specific ways to achieve. Of a given switchingpower supply is concerned, but also protection from the whole to consid er the following points:1) The switching regulator used in the switching transistor in the DC secu rity restrictions on the work of regional work. The transistor switches sel ected by the manual available transistors get DC safe working area. Accor ding to the maximum collector current to determine the input value of o ver-current protection. However, the instantaneous maximum value sho uld be converted to the average current. At rated output current and out put voltage conditions, the switch of the dynamic load line does not exce ed a safe working area DC maximum input voltage, input over-voltage pr otection is the voltage value.2) The switching regulator output limit given by the technical indicators within. Work within the required temperature range, the switching regul ator's output voltage, the lower limit of the output is off, due to the volta ge value of voltage protection. Over-current protection can be based on t he maximum output current to determine. False alarm in order not to pr otect the value of a certain margin to remain appropriate.3) From the above two methods to determine the protection after the p ower supply device in accordance with the needs of measures to determi ne the alarm. Measures the general alarm sound and light alarm two poli ce. Voice of the police applied to more complex machines, power supply parts and do not stand out in a place, it can give staff an effective warning of failure; optical Police instructions can be eye-catching and fault alar m and pointed out that the fault location and type. Protection measur es should be protected as to determine the location. In the high-power, multi-channel power supply, always paying, DC circuit breakers, relays, et c. high-sensitivity auto-protection measures, to cut off the input power s upply to stop working the system from damage. Through the logic contro l circuit to make the appropriate program cut-off switch transistor is sens itive it is convenient and economic. This eliminated large, long response t ime, the price of your high-power relay or circuit breaker.4) The power of putting in the protection circuit will be affected after the reliability of the system, for which want to protect the reliability of the ci rcuit itself is higher in order to improve the reliability of the entire power system, thereby increasing its own power supply MTBF. This requires the protection of strict logic, the circuit is simple, at least components, In ad dition to the protection circuit should also be considered a failure of mai ntenance of their difficulty and their power to protect the damage. The refore, we must be comprehensive and systematic consideration of a vari ety of switching power supply protection measures to ensure the normal operation of switching power supplies and high-efficiency and high relia bility.直流开关稳压电源的保护技术摘要：讨论了直流开关稳压电源的保护系统,提出保护系统设计的原则和整机保护的措施，分析了开关稳压电源中的各种保护的特点及其设计方法,介绍了几种实用保护电路。

1 Power Electronic ConceptsPower electronics is a rapidly developing technology. Components are tting higher current and voltage ratings, the power losses decrease and the devices become more reliable. The devices are also very easy tocontrol with a mega scale power amplification. The prices are still going down pr. kVA and power converters are becoming attractive as a mean to improve the performance of a wind turbine. This chapter will discuss the standard power converter topologies from the simplest converters for starting up the turbine to advanced power converter topologies, where the whole power is flowing through the converter. Further, different park solutions using power electronics arealso discussed.1.1 Criteria for concept evaluationThe most common topologies are selected and discussed in respect to advantages and drawbacks. Very advanced power converters, where many extra devices are necessary in order to get a proper operation, are omitted.1.2 Power convertersMany different power converters can be used in wind turbine applications. In the case of using an induction generator, the power converter has to convert from a fixed voltage and frequency to a variable voltage and frequency. This may be implemented in many different ways, as it will be seen in the next section. Other generator types can demand other complex protection. However, the most used topology so far is a soft-starter, which is used during start up in order to limit the in-rush current and thereby reduce the disturbances to the grid.1.2.1 Soft starterThe soft starter is a power converter, which has been introduced to fixedspeed wind turbines to reduce the transient current during connection or disconnection of the generator to the grid. When the generator speed exceeds the synchronous speed, the soft-starter is connected. Using firing angle control of the thyristors in the soft starter the generator is smoothly connected to the grid over a predefined number of grid periods. An example of connection diagram for the softstarter with a generator is presented in Figure1.Figure 1. Connection diagram of soft starter with generators.The commutating devices are two thyristors for each phase. These are connected in anti-parallel. The relationship between the firing angle (﹤) and the resulting amplification of the soft starter is non-linear and depends additionally on the power factor of the connected element. In the case of a resistive load, may vary between 0 (full on) and 90 (full off) degrees, in the case of a purely inductive load between 90 (full on) and 180 (full off) degrees. For any power factor between 0 and 90 degrees, w ill be somewhere between the limits sketched in Figure 2.Figure 2. Control characteristic for a fully controlled soft starter.When the generator is completely connected to the grid a contactor (Kbyp) bypass the soft-starter in order to reduce the losses during normal operation. The soft-starter is very cheap and it is a standard converter in many wind turbines.1.2.2 Capacitor bankFor the power factor compensation of the reactive power in the generator, AC capacitor banks are used, as shown in Figure 3. The generators are normally compensated into whole power range. The switching of capacitors is done as a function of the average value of measured reactive power during a certain period.Figure 3. Capacitor bank configuration for power factor compensation ina wind turbine.The capacitor banks are usually mounted in the bottom of the tower or in thenacelle. In order to reduce the current at connection/disconnection of capacitors a coil (L) can be connected in series. The capacitors may be heavy loaded and damaged in the case of over-voltages to the grid and thereby they may increase the maintenance cost.1.2.3 Diode rectifierThe diode rectifier is the most common used topology in power electronic applications. For a three-phase system it consists of six diodes. It is shown in Figure 4.Figure 4. Diode rectifier for three-phase ac/dc conversionThe diode rectifier can only be used in one quadrant, it is simple and it is notpossible to control it. It could be used in some applications with a dc-bus.1.2.4 The back-to-back PWM-VSIThe back-to-back PWM-VSI is a bi-directional power converter consisting of two conventional PWM-VSI. The topology is shown in Figure 5.To achieve full control of the grid current, the DC-link voltage must be boosted to a level higher than the amplitude of the grid line-line voltage. The power flow of the grid side converter is controlled in orderto keep the DC-link voltage constant, while the control of the generator side is set to suit the magnetization demand and the reference speed. The control of the back-to-back PWM-VSI in the wind turbine application is described in several papers (Bogalecka, 1993), (Knowles-Spittle et al., 1998), (Pena et al., 1996), (Yifan & Longya, 1992), (Yifan & Longya, 1995).Figure 5. The back-to-back PWM-VSI converter topology.1.2.4.1 Advantages related to the use of the back-to-back PWM-VSIThe PWM-VSI is the most frequently used three-phase frequency converter. As a consequence of this, the knowledge available in the field is extensive and well established. The literature and the available documentation exceed that for any of the other converters considered in this survey. Furthermore, many manufacturers produce components especially designed for use in this type of converter (e.g., a transistor-pack comprising six bridge coupled transistors and anti paralleled diodes). Due to this, the component costs can be low compared to converters requiring components designed for a niche production.A technical advantage of the PWM-VSI is the capacitor decoupling between the grid inverter and the generator inverter. Besides affording some protection, this decoupling offers separate control of the two inverters, allowing compensation of asymmetry both on the generator side and on the grid side, independently.The inclusion of a boost inductance in the DC-link circuit increases the component count, but a positive effect is that the boost inductance reduces the demands on the performance of the grid side harmonic filter, and offers some protection of the converter against abnormal conditions on the grid.1.2.4.2 Disadvantages of applying the back-to-back PWM-VSIThis section highlights some of the reported disadvantages of the back-to-back PWM-VSI which justify the search for a more suitable alternative converter:In several papers concerning adjustable speed drives, the presence of the DC link capacitor is mentioned as a drawback, since it is heavy and bulky, it increases the costs and maybe of most importance, - it reduces the overall lifetime of the system. (Wen-Song & Ying-Yu, 1998); (Kim & Sul, 1993); (Siyoung Kim et al., 1998).Another important drawback of the back-to-back PWM-VSI is the switching losses. Every commutation in both the grid inverter and the generator inverter between the upper and lower DC-link branch is associated with a hard switching and a natural commutation. Since the back-to-back PWM-VSI consists of two inverters, the switching losses might be even more pronounced. The high switching speed to the grid may also require extra EMI-filters.To prevent high stresses on the generator insulation and to avoid bearing current problems (Salo & Tuusa, 1999), the voltage gradient may have to be limited by applying an output filter.1.2.5 Tandem converterThe tandem converter is quite a new topology and a few papers only have treated it up till now ((Marques & Verdelho, 1998); (Trzynadlowski et al., 1998a); (Trzynadlowski et al., 1998b)). However, the idea behind the converter is similar to those presented in ((Zhang et al., 1998b)), where the PWM-VSI is used as an active harmonic filter to compensate harmonic distortion. The topology of the tandem converter is shown inFigure 6.Figure 6. The tandem converter topology used in an induction generator wind turbine system.The tandem converter consists of a current source converter, CSC, in thefollowing designated the primary converter, and a back-to-back PWM-VSI, designated the secondary converter. Since the tandem converter consists of four controllable inverters, several degrees of freedom exist which enable sinusoidal input and sinusoidal output currents. However, in this context it is believed that the most advantageous control of the inverters is to control the primary converter to operate in square-wave current mode. Here, the switches in the CSC are turned on and off only once per fundamental period of the input- and output current respectively. In square wave current mode, the switches in the primary converter may either be GTO.s, or a series connection of an IGBT and a diode.Unlike the primary converter, the secondary converter has to operateat a high switching frequency, but the switched current is only a small fraction of the total load current. Figure 7 illustrates the current waveform for the primary converter, the secondary converter, is, and the total load current il.In order to achieve full control of the current to/from the back-to-back PWMVSI, the DC-link voltage is boosted to a level above the grid voltage. As mentioned, the control of the tandem converter is treated in only a few papers. However, the independent control of the CSC and the back-to-back PWM-VSI are both well established, (Mutschler & Meinhardt, 1998); (Nikolic & Jeftenic, 1998); (Salo & Tuusa, 1997); (Salo & Tuusa, 1999).Figure 7. Current waveform for the primary converter, ip, the secondary converter, is, and the total load current il.1.2.5.1Advantages in the use of the Tandem ConverterThe investigation of new converter topologies is commonly justifiedby thesearch for higher converter efficiency. Advantages of the tandem converter are the low switching frequency of the primary converter, and the low level of the switched current in the secondary converter. It is stated that the switching losses of a tandem inverter may be reduced by 70%, (Trzynadlowski et al., 1998a) in comparison with those of an equivalent VSI, and even though the conduction losses are higher for the tandem converter, the overall converter efficiency may be increased.Compared to the CSI, the voltage across the terminals of the tandem converter contains no voltage spikes since the DC-link capacitor of the secondary converter is always connected between each pair of input- and output lines (Trzynadlowski et al., 1998b).Concerning the dynamic properties, (Trzynadlowski et al., 1998a) states that the overall performance of the tandem converter is superior to both the CSC and the VSI. This is because current magnitude commands are handled by the voltage source converter, while phase-shift current commands are handled by the current source converter (Zhang et al., 1998b).Besides the main function, which is to compensate the current distortion introduced by the primary converter, the secondary converter may also act like an active resistor, providing damping of the primary inverter in light load conditions (Zhang et al., 1998b).1.2.5.2 Disadvantages of using the Tandem ConverterAn inherent obstacle to applying the tandem converter is the high number of components and sensors required. This increases the costs and complexity of both hardware and software. The complexity is justified by the redundancy of the system (Trzynadlowski et al., 1998a), however the system is only truly redundant if a reduction in power capability and performance is acceptable.Since the voltage across the generator terminals is set by the secondary inverter, the voltage stresses at the converter are high.Therefore the demands on the output filter are comparable to those when applying the back-to-back PWM-VSI.In the system shown in Figure 38, a problem for the tandem converter in comparison with the back-to-back PWM-VSI is the reduced generator voltage. By applying the CSI as the primary converter, only 0.866% of the grid voltage can be utilized. This means that the generator currents (and also the current through the switches) for the tandem converter must be higher in order to achieve the same power.1.2.6 Matrix converterIdeally, the matrix converter should be an all silicon solution with no passive components in the power circuit. The ideal conventional matrix converter topology is shown in Figure 8.Figure 8. The conventional matrix converter topology.The basic idea of the matrix converter is that a desired input current (to/from the supply), a desired output voltage and a desired output frequency may be obtained by properly connecting the output terminals of the converter to the input terminals of the converter. In order to protect the converter, the following two control rules must be complied with: Two (or three) switches in an output leg are never allowed to be on at the same time. All of the three output phases must be connected to an input phase at any instant of time. The actual combination of the switchesdepends on the modulation strategy.1.2.6.1 Advantages of using the Matrix ConverterThis section summarises some of the advantages of using the matrix converter in the control of an induction wind turbine generator. For a low output frequency of the converter the thermal stresses of the semiconductors in a conventional inverter are higher than those in a matrix converter. This arises from the fact that the semiconductors in a matrix converter are equally stressed, at least during every period of the grid voltage, while the period for the conventional inverter equals the output frequency. This reduces thethermal design problems for the matrix converter.Although the matrix converter includes six additional power switches compared to the back-to-back PWM-VSI, the absence of the DC-link capacitor may increase the efficiency and the lifetime for the converter (Schuster, 1998). Depending on the realization of the bi-directional switches, the switching losses of the matrix inverter may be less than those of the PWM-VSI, because the half of the switchings become natural commutations (soft switchings) (Wheeler & Grant, 1993).1.2.6.2 Disadvantages and problems of the matrix converterA disadvantage of the matrix converter is the intrinsic limitation of the output voltage. Without entering the over-modulation range, the maximum output voltage of the matrix converter is 0.866 times the input voltage. To achieve the same output power as the back-to-back PWM-VSI, the output current of the matrix converter has to be 1.15 times higher, giving rise to higher conducting losses in the converter (Wheeler & Grant, 1993).In many of the papers concerning the matrix converter, the unavailability of a true bi-directional switch is mentioned as one of the major obstacles for the propagation of the matrix converter. In the literature, three proposals for realizing a bi-directional switch exists. The diode embedded switch (Neft & Schauder, 1988) which acts like a truebi-directional switch, the common emitter switch and the common collector switch (Beasant et al., 1989).Since real switches do not have infinitesimal switching times (which is not desirable either) the commutation between two input phases constitutes a contradiction between the two basic control rules of the matrix converter. In the literature at least six different commutation strategies are reported, (Beasant et al., 1990); (Burany, 1989); (Jung & Gyu, 1991); (Hey et al., 1995); (Kwon et al., 1998); (Neft & Schauder, 1988). The most simple of the commutation strategies are those reported in (Beasant et al., 1990) and (Neft & Schauder, 1988), but neither of these strategies complies with the basic control rules.译文1 电力电子技术的内容电力电子技术是一门正在快速发展的技术,电力电子元器件有很高的额定电流和额定电压,它的功率减小元件变得更加可靠、耐用.这种元件还可以用来控制比它功率大很多倍的元件。

电子类文献中英文翻译(发电机)DC GENENRATORS1. INTRODUCTIONFor all practical purposes, the direct-current generator is only used for special applications and local dc power generation. This limitation is due to the commutator required to rectify the internal generated ac voltage, thereby making largescale dc power generators not feasible.Consequently, all electrical energy produced commercially is generated and distributed in the form of three-phase ac power. The use of solid state converters nowadays makes conversion to dc economical. However, the operating characteristics of dc generators are still important, because most concepts can be applied to all other machines.2. FIELD WINDING CONNECTIONSThe general arrangement of brushes and field winding for a four-pole machine is as shown in Fig.1. The four brushes ride on the commutator. The positive brusher are connected to terminal A1 while the negative brushes are connected to terminal A2 of the machine. As indicated in the sketch, the brushes are positioned approximately midway under the poles. They make contact with coils that have little or no EMF induced in them, since their sides are situated between poles.Figure 1 Sketch of four-pole dc matchineThe four excitation or field poles are usually joined in series and their ends brought out to terminals marked F1 and F2. They are connected such that they produce north and south poles alternately.The type of dc generator is characterized by the manner in which the field excitation is provided. In general, the method employed to connect the field and armature windings falls into the following groups (see Fig.2):Figure2 Field connections for dc generators:(a)separately excited generator;(b)self-excited,shunt generator;(c)series generator;(d)compound generator;short-shunt connection;(e)compoundgenerator,long-shunt connection.The shunt field contains many turns of relatively fine wire and carries a comparatively small current, only a few percent of rated current. The series field winding, on the other hand, has few turns of heavy wire since it is in series with the armature and therefore carries the load current.Before discussing the dc generator terminal characteristics, let us examine the relationship between the generated voltage and excitation current of a generator on no load. The generated EMF is proportional to both the flux per pole and the speed at which the generator is driven, EG=kn. By holding the speed constant it can be shown the EG depends directly on the flux.To test this dependency on actual generators is not very practical, as it involves a magnetic flux measurement. The flux is produced by the ampere-turns of the field coils: in turn, the flux must depend on the amount of field current flowing since the number of turns on the field winding is constant. This relationship is not linear because of magnetic saturation after the field current reaches a certain value. The variation of EG versus the field current If may be shown by a curve known as the magnetization curve or open-circuit characteristic. For this a given generator is driven at a constant speed, is not delivering load current, and has its field winding separately excited.The value of EG appearing at the machine terminals is measured as If is progressively increased from zero to a value well above rated voltage of that machine. The resulting curve is shown is Fig.3. When Ij=0, that is, with the field circuit open circuited, a small voltage Et is measured, due to residual magnetism. As the field current increases, the generated EMF increases linearly up to the knee of the magnetization curve. Beyond this point, increasing the field current still further causes saturation of the magnetic structure to set in.Figure 3 Magnetization curve or open-circuit characteristic of a separately excited dc machineThe means that a larger increase in field current is required to produce a given increase in voltage.Since the generated voltage EG is also directly proportional to the speed, a magnetization curve can be drawn for any other speed once the curve is determined. This merely requires anadjustment of all points on the curve according ton n x E E G G ''=where the quantities values at the various speeds.3. VOLTAGE REGULATIONLet us next consider adding a load on generator. The terminal voltage will then decrease (because the armature winding ha resistance) unless some provision is made to keep it constant. A curve that shows the value of terminal voltage for various load currents is called the load or characteristic of the generator.Figure 4 (a) directs current it to urge the generator load characteristics; (b) circuit diagramFig.4 shows the external characteristic of a separately excited generator. The decrease in the terminal voltage is due mainly to the armature circuit resistance RA. In general,A A G t R I E V -=where Vt is the terminal voltage and IA is the armature current (or load current IL) supplied by the generator to the load.Another factor that contributes to the decrease in terminal voltage is the decrease in flux due to armature reaction. The armature current established an MMF that distorts the main flux, resulting in a weakened flux, especially in noninterpole machines. This effect is calledarmature reaction. As Fig.4 shows, the terminal voltage versus load current curve does not drop off linearly since the iron behaves nonlinear. Because armature reaction depends on the armature current it gives the curve its drooping characteristic.4. SHUNT OR SELF-EXCIITED GENRATORSA shunt generator has its shunt field winding connected in parallel with the armature so that the machine provides its own excitation, as indicated in Fig.5. The question arises whether the machine will generate a voltage and what determines the voltage.For voltage to “build up” as it is called, there must be some remanent magnetism in the field poles. Ordinarily, if the generator has been used previously, there will be some remanent magnetism. We have seen in Section 3 that if the field would be disconnected, there will be small voltage Ef generated due to this remanent magnetism, provided that the generator is driven at some speed. Connecting the field for self-excitation, this small voltage will be applied to the shunts field and drive a small current through the field circuit. If this resulting small current in the shunt field is of such a direction that it weakens the residual flux, the voltage remains near zero and the terminal voltage does not build up. In this situation the weak main pole flux opposes the residual flux.Figure 5 Shunt generator:(a)circuit;(b)load characteristicIf the connection is such that the weak main pole flux aids the residual flux, the inducedvoltage increases rapidly to a large, constant value. The build-up process is readily seen to be cumulanve. That is, more voltage increases the field current, which in turn increases the voltage, and so on. The fact that this process terminates at a finite voltage is due to the nonlinear behavior of the magnctic circuit. In steady state the generated voltage is causes a field current to flow that is just sufficient to develop a flux required for the generated EMF that causes the field current to flow.The circuit carries only dc current, so that the field current depends only on the field circuit resistance, Rf. This may consist of the field circuit resistance Rf, the field current depends on the generated voltage in accordance with Ohm ’s law.It should be evident that on a new machine or one that has lost its residual flux because of a long idle period, some magnetism must be created. This is usually done by connecting the field winding only to a separate dc source for a few seconds. This procedure is generally known as flashing the field.Series GeneratorsAs mentioned previously, the field winding of a series generator is in series with the armature. Since it carries the load current the series field winding consists of only a few turns of thick wire. At no load, the generated voltage is small due to residual field flux only. When a load is added, the flux increases, and so does the generated voltage. Fig.7 shows the load characteristic of a series generator driven at a certain speed. The dashed line indicates the generated EMF of the same machine with the armature open-circuited and the field separately excited. The difference between the two curves is simply the IR drop in the series field and armature winding, such that)(S A A G t R R I E V +-=where RS is the series field winding resistance.Figure 7 Series generator: (a)circuit diagram;(b)load characteristicsCompound GeneratorsThe compound generator has both a shunt and a series field winding, the latter winding wound on top of the shunt winding. Fig.8 shows the circuit diagram. The two windings are usually connected such that their ampere-turns act in the same direction. As such the generator is said to be cumulatively compounded.The shunt connection illustrated in Fig.8 is called a long shunt connection. If the shunt field winding is directly connected across the armature terminals, the connection is referred to as a short shunt. In practice the connection used is of little consequence, since the shunt field winding carries a small current compared to the full-load current. Furthermore, the number of turns on the series field winding. This implies it has a low resistance value and the corresponding voltage drop across it at full load is minimal.Curves in Fig.9 represents the terminal characteristic of the shunt field winding alone. By the addition of a small series field winding the drop in terminal voltage with increased loading is reduced as indicated. Such a generator is said to be undercompounded. By increasing the number of series turns, the no-load and full-load terminal voltage can be made equal; the generator is then said to be flatcompounded. If the number of series turns is more than necessary to compensate for the voltage drop, the generator is overcome pounded. In that case the full-load voltage is higher than the no-load voltage.Figure 9 Terminal characteristics of compound generators compared with that of the shunt generatorThe overcompounded generator may be used in instances where the load is at some distance from the generator. The voltage drops in the feeder lines are the compensated for with increased loading. Reversing the polarity of the series field in relation to the shunt field, the fields will oppose each other more and more as the load current increase. Such a generator is said to be differentially compounded. It is used in applications where feeder lines could occur approaching those of a short circuit. An example would be where feeder lines could break and short circuit the generator. The short-circuit current, however, is then limited to a “safe” value. The terminal characteristic for this type of generator is also shown in Fig.9. Compound generators are used more extensively than the other types because they may be designed to have a wide varity of terminal characteristics.As illustrated, the full-load terminal voltage can be maintained at the no-load value by the proper degree of compounding. Other methods of voltage control are the use of rheostats, for instance, in the field circuit. However, with changing loads it requires a constant adjustment of the field rheostat to maintain the voltage. A more useful arrangement, which is now common practice, is to use an automatic voltage regulator with the generator. In essence, the voltage regulator is a feedback control system. The generator output voltage is sensed and compared to a fixed reference voltage deviation from the reference voltage gives an error signal that is fed to a power amplifier. The power amplifier supplies the field excitation current. If the error signal is positive, for example, the output voltage is larger than desiredand the amplifier will reduce its current drive. In doing so the error signal will be reduced to zero.TRANSFORMER1. INTRODUCTIONThe high-voltage transmission was need for the case electrical power is to be provided at considerable distance from a generating station. At some point this high voltage must be reduced, because ultimately is must supply a load. The transformer makes it possible for various parts of a power system to operate at different voltage levels. In this paper we discuss power transformer principles and applications.2. TOW-WINDING TRANSFORMERSA transformer in its simplest form consists of two stationary coils coupled by a mutual magnetic flux. The coils are said to be mutually coupled because they link a common flux. In power applications, laminated steel core transformers (to which this paper is restricted) are used. Transformers are efficient because the rotational losses normally associated with rotating machine are absent, so relatively little power is lost when transforming power from one voltage level to another. Typical efficiencies are in the range 92 to 99%, the higher values applying to the larger power transformers.The current flowing in the coil connected to the ac source is called the primary winding or simply the primary. It sets up the flux φ in the core, which varies periodically both in magnitude and direction. The flux links the second coil, called the secondary winding or simply secondary. The flux is changing; therefore, it induces a voltage in the secondary by electromagnetic induction in accordance with Lenz’s law. Thus the primary receives its power from the source while the secondary supplies this power to the load. This action is known as transformer action.3. TRANSFORMER PRINCIPLESWhen a sinusoidal voltage V p is applied to the primary with the secondary open-circuited, there will be no energy transfer. The impressed voltage causes a small current Iθ to flow in the primary winding. This no-load current has two functions: (1) it produces the magnetic flux in the core, which varies sinusoidally between zero and φm, where φm is the maximum value of the core flux; and (2) it provides a component to account for the hysteresis and eddy current losses in the core. There combined losses are normally referred to as the core losses.The no-load current Iθ is usually few percent of the rated full-load current of the transformer (about 2 to 5%). Since at no-load the primary winding acts as a large reactance due to the iron core, the no-load current will lag the primary voltage by nearly 90º. It is readily seen that the current component I m= I0sinθ0, called the magnetizing current, is 90ºin phase behind the primary voltage V P. It is this component that sets up the flux in the core; φ is therefore in phase with I m.The second component, I e=I0sinθ0, is in phase with the primary voltage. It is the current component that supplies the core losses. The phasor sum of these two components represents the no-load current, orI0 = I m+ I eIt should be noted that the no-load current is distortes and nonsinusoidal. This is the result of the nonlinear behavior of the core material.If it is assumed that there are no other losses in the transformer, the induced voltage In the primary, E p and that in the secondary, E s can be shown. Since the magnetic flux set up by the primary winding，there will be an induced EMF E in the secondary winding in accordance with Faraday’s law, namely, E=NΔφ/Δt. This same flux also links the primary itself, inducing in it an EMF, E p. As discussed earlier, the induced voltage must lag the flux by 90º, therefore, they are 180º out of phase with the applied voltage. Since no current flows in the secondary winding, E s=V s. The no-load primary current I0 is small, a few percent of full-load current. Thus the voltage in the primary is small and V p is nearly equal to E p. The primary voltage and the resulting flux are sinusoidal; thus the induced quantities E p and E s vary as a sine function. The average value of the induced voltage given byE avg = turns× change in flux in a given time given timewhich is Faraday’s law applied to a finite time interval. It follows thatE avg = N 21/(2)m f = 4fNφm which N is the number of turns on the winding. Form ac circuit theory, the effective or root-mean-square (rms) voltage for a sine wave is 1.11 times the average voltage; thusE = 4.44fNφmSince the same flux links with the primary and secondary windings, the voltage per turn in each winding is the same. HenceE p = 4.44fN p φmandE s = 4.44fN s φmwhere E p and Es are the number of turn on the primary and secondary windings, respectively. The ratio of primary to secondary induced voltage is called the transformation ratio. Denoting this ratio by a, it is seen that a = p sE E = p s N N Assume that the output power of a transformer equals its input power, not a bad sumption in practice considering the high efficiencies. What we really are saying is that we are dealing with an ideal transformer; that is, it has no losses. ThusP m = P outorV p I p × primary PF = V s I s × secondary PFwhere PF is the power factor. For the above-stated assumption it means that the power factor on primary and secondary sides are equal; thereforeV p I p = V s I s from which is obtainedp s V V = p s I I ≌ p sE E ≌ aIt shows that as an approximation the terminal voltage ratio equals the turns ratio. The primary and secondary current, on the other hand, are inversely related to the turns ratio. The turns ratio gives a measure of how much the secondary voltage is raised or lowered in relation to the primary voltage. To calculate the voltage regulation, we need more information.The ratio of the terminal voltage varies somewhat depending on the load and its power factor. In practice, the transformation ratio is obtained from the nameplate data, which list the primary and secondary voltage under full-load condition.When the secondary voltage V s is reduced compared to the primary voltage, the transformation is said to be a step-down transformer: conversely, if this voltage is raised, it is called a step-up transformer. In a step-down transformer the transformation ratio a is greater than unity (a>1.0), while for a step-up transformer it is smaller than unity (a<1.0). In the event that a=1, the transformer secondary voltage equals the primary voltage. This is a special type of transformer used in instances where electrical isolation is required between the primary and secondary circuit while maintaining the same voltage level. Therefore, this transformer is generally knows as an isolation transformer.As is apparent, it is the magnetic flux in the core that forms the connecting link between primary and secondary circuit. In section 4 it is shown how the primary winding current adjusts itself to the secondary load current when the transformer supplies a load.Looking into the transformer terminals from the source, an impedance is seen which by definition equals V p / I p . From p s V V = p s I I ≌ p sE E ≌ a , we have V p = aV s and I p = I s /a.In terms of V s and I s the ratio of V p to I p isp p V I = /s s aV I a= 2s s a V I But V s / I s is the load impedance Z L thus we can say thatZ m (primary) = a 2Z LThis equation tells us that when an impedance is connected to the secondary side, it appears from the source as an impedance having a magnitude that is a 2 times its actual value. We say that the load impedance is reflected or referred to the primary. It is this property oftransformers that is used in impedance-matching applications.4. TRANSFORMERS UNDER LOADThe primary and secondary voltages shown have similar polarities, as indicated by the “dot-making” convention. The dots near the upper ends of the windings have the same meaning as in circuit theory; the marked terminals have the same polarity. Thus when a load is connected to the secondary, the instantaneous load current is in the direction shown. In other words, the polarity markings signify that when positive current enters both windings at the marked terminals, the MMFs of the two windings add.Since the secondary voltage depends on the core flux φ0, it must be clear that the flux should not change appreciably if E s is to remain essentially constant under normal loading conditions. With the load connected, a current I s will flow in the secondary circuit, because the induced EMF E s will act as a voltage source. The secondary current produces an MMF N s I s that creates a flux. This flux has such a direction that at any instant in time it opposes the main flux that created it in the first place. Of course, this is Lenz’s law in action. Thus the MMF represented by N s I s tends to reduce the core flux φ0. This means that the flux linking the primary winding reduces and consequently the primary induced voltage E p, This reduction in induced voltage causes a greater difference between the impressed voltage and the counter induced EMF, thereby allowing more current to flow in the primary. The fact that primary current I p increases means that the two conditions stated earlier are fulfilled: (1) the power input increases to match the power output, and (2) the primary MMF increases to offset the tendency of the secondary MMF to reduce the flux.In general, it will be found that the transformer reacts almost instantaneously to keep the resultant core flux essentially constant. Moreover, the core flux φ0drops very slightly between n o load and full load (about 1 to 3%), a necessary condition if E p is to fall sufficiently to allow an increase in I p.On the primary side, I p’ is the current that flows in the primary to balance the demagnetizing effect of I s. Its MMF N p I p’ se ts up a flux linking the primary only. Since the core flux φ0 remains constant. I0 must be the same current that energizes the transformer at no load. Theprimary current I p is therefore the sum of the current I p’ and I0.Because the no-load current is relatively small, it is correct to assume that the primary ampere-turns equal the secondary ampere-turns, since it is under this condition that the core flux is essentially constant. Thus we will assume that I0 is negligible, as it is only a small component of the full-load current.When a current flows in the secondary winding, the resulting MMF (N s I s) creates a separate flux, apart from the flux φ0 produced by I0, which links the secondary winding only. This flux does no link with the primary winding and is therefore not a mutual flux.In addition, the load current that flows through the primary winding creates a flux that links with the primary winding only; it is called the primary leakage flux. The secondary- leakage flux gives rise to an induced voltage that is not counter balanced by an equivalent induced voltage in the primary. Similarly, the voltage induced in the primary is not counterbalanced in the secondary winding. Consequently, these two induced voltages behave like voltage drops, generally called leakage reactance voltage drops. Furthermore, each winding has some resistance, which produces a resistive voltage drop. When taken into account, these additional voltage drops would complete the equivalent circuit diagram of a practical transformer. Note that the magnetizing branch is shown in this circuit, which for our purposes will be disregarded. This follows our earlier assumption that the no-load current is assumed negligible in our calculations. This is further justified in that it is rarely necessary to predict transformer performance to such accuracies. Since the voltage drops are all directly proportional to the load current, it means that at no-load conditions there will be no voltage drops in either winding.中文翻译①直流发电机1.介绍关于所有实际目的来说，直流发电机仅用于特殊场合与地方性发电厂。

中英文对照外文翻译文献(文档含英文原文和中文翻译)外文文献：Circuit BreaksWithin a few years of the introduction of the fuse，the growing electrical industry started looking for an alternative method of providing protection for electric circuits．They wanted a device that would not bedestroyed by its operation，that could simply be reset to restore power, and that could also be used as a means of switching for the circuit．Out of this development work came the circuit breaker．which is an electromechanical device．The circuit breaker is defined as a device designed to open and close a circuit by non-automatic means and to open the circuit automatically on a predetermined over-current without injure to itself when properly applied within its rating.As with other equipment，circuit breakers are divided into those rated for 1 000 volts and less and those rated for more than 1000 volts．Low-voltage circuit breakers were also divided into two distinct categories，molded-case and power types．However，in the past few years the distinction between these two types has become less clea-cut as a new type of encased breaker are universally operated in air, so it is not necessary to designate them as air circuit breakers as this understood．Medium and high—voltage breakers，on the other hand，use mediums other than air in which to open the circuit and therefore must be designated as being air, gas，and so on．Apart from having different voltage and continuous currentratings．breakers have widely different interrupting ratings，response characteristics，and methods of operation．The proper application of circuit breakers requires a good knowledge of all the characteristics and options available for each type．The simplest circuit—opening device is the manually operated knife switch．This switch has the basic parts required of any circuit—opening device：a fixed contact, a moving，an operating handle，and a base—plate or flame．However as anyone who has opened a knife switch under load has witnessed，there is a luminous discharge drawn between the separating contacts of the switch．This discharge is called an arc，and it consists of a stream of positive and negative ions. The current flowing in a circuit cannot be instantaneously interrupted．As a result，the arc continues until the switch contacts have separated far enough to finally extinguish the arc．The arc can make the opening of the switch very unsafe and unreliable when interrupting a circuit breaker must provide a safer and more reliable interrupting action. The following are the means by witch low—voltage circuit breakers can be made to safely interrupt large faultcurrents with a minimum of contact damage．1．Fast speed of operation．The duration and severity of an arc depends in part on the speed with witch the contacts can be separated，therefore powerful spring are used to rapidly force the contacts open．These springs are compressed (charged)during the closing operation．The breaker contacts are then mechanically held closed and are released by a separate trip mechanism．An operator can initiate the opening of the breaker but has no control over the speed with which the contacts separate．2．Use of arcing contacts．The arc burn can cause pitting，which eventually affects the ability of the contacts to carry the load current when closed．To offset this, two parallel sets of contacts are used for each pole of the breaker，a main current carrying set and an auxiliary or arcing set．When the breaker is tripped open, the main contacts separate first，transferring the current flow to the arcing contacts．The arcing contacts then separate a split second late，drawing the arc between them and leaving the main contacts free of any arcing．This allows the surfaces of the main current carrying contacts to be made of high—conductivitymetal such as silver，the surfaces of the arcing contacts are then made of a tougher alloy better able to withstand the effects of arcing．3．Use of arc chutes Parallel plates enclosed in the form of a chute are mounted directly above the arcing contacts．As the arcing contacts separate, the resulting are creates a strong magnetic field that forces the arc upward into the plates．The arc stream is then broken into a series of small arcs，which are quickly cooled，deionized，and extinguished．The ionized gases created by the are stream must be deionized before they are expelled from the arc chute；otherwise，secondary arcing could occur between the line side terminals of the breaker, which are still energized．中文译文：断路器在引入保险丝的这几年，电气行业开始寻找一种保护电路的替代方法。