Electric golf car with low-speed regenerative braking
First Claim
1. A control system for controlling the current and voltage of an electric shunt wound motor associated with an electric vehicle, said motor including an armature coil and a field coil, said system comprising:
- a plurality of switching devices electrically coupled in an H-bridge circuit and electrically coupled to the field coil;
a plurality of switching devices electrically coupled in a half H-bridge circuit, wherein a first switching device Is electrically coupled in parallel with the armature coil and a second switching device is electrically coupled in series with the armature coil; and
a freewheel diode electrically coupled in parallel with the armature coil; and
means for measuring armature current in a negative quadrant of a field coil map, said system selecting a field coil current for controlling the field coil based on the measured armature current.
2 Assignments
0 Petitions
Accused Products
Abstract
A control system for an electric vehicle, such as a golf car, that includes a plurality of power MOSFETs. The vehicle includes a shunt wound motor including an armature coil and a field coil. One of the MOSFETs is connected in parallel across the armature coil and another MOSFET is connected in series with the armature coil. The MOSFET across the armature coil includes a freewheel diode. When the motor is operating below its base speed, i.e., when the back EMF is below the power supply voltage, a current flow can be induced by momentarily turning on the series MOSFET, shorting the armature coil. Because of the residual inductance in the motor, a current flow in the counter clockwise direction is initiated at which point the series MOSFET is turned off. Consequently, a large voltage spike across the motor occurs which results in current flow back into the battery pack. By quickly turning the series MOSFET on and off the current flow can be maintained, and the regenerative braking can occur even at slow speeds. The control system also allows the vehicle to be operated at speeds below its base speed, and provide field current control by measuring the armature current in the negative quadrant of the field map.
43 Citations
24 Claims
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1. A control system for controlling the current and voltage of an electric shunt wound motor associated with an electric vehicle, said motor including an armature coil and a field coil, said system comprising:
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a plurality of switching devices electrically coupled in an H-bridge circuit and electrically coupled to the field coil;
a plurality of switching devices electrically coupled in a half H-bridge circuit, wherein a first switching device Is electrically coupled in parallel with the armature coil and a second switching device is electrically coupled in series with the armature coil; and
a freewheel diode electrically coupled in parallel with the armature coil; and
means for measuring armature current in a negative quadrant of a field coil map, said system selecting a field coil current for controlling the field coil based on the measured armature current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An electric golf car including a braking system, a battery system and a shunt wound motor, said motor having an armature coil and a field coil, said golf car comprising:
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a plurality of MOSFET devices electrically coupled in a H-bridge circuit and electrically coupled to the field coil;
a plurality of MOSFET devices electrically coupled in a half H-bridge circuit, wherein a first MOSFET device is electrically coupled in parallel with the armature coil and a second MOSFET device is electrically coupled in series with the armature coil;
a freewheel diode electrically coupled in parallel with the armature coil;
a current sensor for measuring armature current through the armature coil;
a speed pedal position switch for determining the position of an accelerator pedal of the golf car, said pedal position switch generating a speed reference signal; and
a control system, said control system switching the first MOSFET device on and off so as to control the armature current traveling through the armature coil to provide regenerative braking of the speed of the golf oar from a base speed to zero, wherein the control system includes means for measuring armature current in a negative quadrant of a field coil map, said control system selecting a field coil current for controlling the field coil based on the measured armature current. - View Dependent Claims (13, 14, 15, 16)
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17. A method of controlling the speed of an electric vehicle, said electric vehicle including a shunt wound motor having an armature coil and a field coil, said method comprising the steps of:
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electrically coupling a first switching device in parallel across the armature coil of the motor;
providing a current path in parallel to the first switching device to dissipate a residual current through the armature;
turning the switching device on and off to control the armature current through the armature coil so as to provide regenerative braking below a base speed of the motor; and
measuring armature current in a negative quadrant of a field map coil, and controlling the field coil current based on the measured armature current. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification