新型的充电器

The device dlescribed in this paper is a microprocessor-based ferroresonant battery charger for EVs. The charger utilizes gassing point detection [2] to determine when to terminate a charge on a set of batteries. The battery charger is designed to delliver a maximum current of 30 A at 150 Vdc to a lead-acid battery pack. The basic operation of the charger is described below. The charger is made up of two main parts, the ferroresonant transformer, and the control circuitry. The charger control circuit consists of the microprocessor, the power electronics isolation and switches, and the voltage monitoring circuit. The control circuit allows t e charger to utilize gassing point h detection to determine when to terminate the application of a charge on a set of batteries. Typically, the device applies voltage to the batteries under charge for one hour. The charge is then interrupted @y the microprocessor turning off a triac betweein the secondary of the ferroresonant transformer arid the bridge rectifier, Fig. 1. After the transformer is disconnected from the battery pack, the microprocessor turns on a MOSFET switch that introduces a resistive load across the terminals of the battery pack.
ABSTRACT
The paper covers the design and testing of a microprocessor-based ferroresonant battery charger. The power delivery section of the charger is a ferroresonant transformer with a rectified output that produces 150 Vdc at 30 A. The charger utilizes gassing point detection to determine when to terminate a charge on a set of batteries. The control section of the battery charger periodically places a resistive load across the battery under charge that allows this change in resistance to be detected. A microprocessor controls the timing and executes the gating of the needed switches in the circuit, and then gathers and analyzes data from the monitor circuit. The charger monitor circuit measures the voltage drop across the battery, which is proportional to the battery intemal resistance, when the load is introduced. Test results indicate that a ferroresonant transformer makes an excellent base for the power delivery section of a high voltage battery charger.
3. FERRORESONANTTRANSFORMER
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The ferroresonant transformer is a form of a voltage regulator [3]. Fig. 2 shows that the primary and secondary sections of the ferroresonant transformer are physically separated by the magnetic shunts. The primary section is made up of only the primary winding, while the secondary section contains the output winding and the resonating winding which is connected to the resonating capacitor. The primary winding operates in the linear portion of the B-H curve while the secondary operates in the saturated mode. The capacitor connected across the secondary determines the resonant characteristics. When the flux density of the transformer secondary winding reactance reaches a maximum the impedance becomes a small saturated inductance. This low impedance forces the capacitor to discharge and recharge to the opposite polarity. Fig. 3 illustrates the output voltage waveform of the ferroresonant transformer given a sinusoidal input; the output is very similar to a squarewave.
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TRANSFORMER
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Fig. 1 Block diagram of charger circuit
0-7803-3243-5 /96/$4.00 0 1996 IEEE
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The response of the battery to this resistive load is evaluated by the monitoring circuitry, and a voltage proportional to the voltage drop at the battery terminals is sent to the A/D of the microprocessor. The microprocessor calculates a running average of these voltage signals, and looks for a noticeable change in the signal which indicates the onset of gassing in the battery pack under charge. After the MOSFET is on for 700 ms, it is turned off and the triac is gated to return the charge voltage to the battery pack. After five minutes of charging, the process repeats.
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A NOVEL MICROPROCESSOR-BASED FXRRORESONANT BATTERY CHARGER FOR ELECTRIC VEHICLES
C.R. Mersman N.G. Dillman M,,M.Morcos Department of Electrical and Computer Engineering Kansas State University Manhattan, Kansas 66506
2. CHARGEROUTLINE
1. INTRODUCTION
In a recent EPRI report [l], a comparison is made between the emissions from a gasoline-powered automobile and pollution generated in powering the same automobile with the internal combustion engine replaced by an electric motor. Results illustrate that carbon monoxide and volatile organic compounds emissions decrease by over 99 % , whereas carbon dioxide decreases by about 50% when the electric vehicle (EV) is used. Because of the increased burning of coal by the utilities to power the EV, emissions of sulfur dioxide increase. A positive result of having all the air pollution generated in the operation of EVs occur at power plants is that pollution can be monitored and corrected easily. Another advantage of switching from gasolinepowered automobiles to electric vehicles is a reduction in the dependency on foreign oil. Only 4%of electricity in the United States is generated by burning oil. The switch from gasoline-powered vehicles to EVs will help reduce the trade deficit.