US 4,423,362 AGranted

Electric vehicle current regulating system

AssigneeGeneral Electric Company

InventorsCharles E. Konrad, Robert C. Clark, deceased

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Abstract

A control system for a separately excited DC electric traction motor in an electrically powered vehicle incorporates a plurality of current limit functions designed to protect both the motor and control electronics. A time dependent current limit is utilized to permit overcurrent conditions for limited time intervals such that additional power can be obtained for sudden torque requirements without having to design the motor or control electronics to function under continuous high torque conditions. The continuous current limit values based on percent conduction time of a thyristor chopper circuit in the control system is modified in response to overheating of the motor and the main switching thyristor, to overvoltage on the thyristor commutating capacitor and to available voltage for powering the motor.

Claims9

Dependent claims

In a control system for a vehicle having an electric traction motor for providing vehicle propulsion power, the control system including a percent conduction time power regulator responsive to a current reference signal to regulate motor current and also including an accelerator for producing a current command signal having a value corresponding to an operator desired value of said current reference signal, the improvement comprising:

(a) means for establishing a first current limit value which varies between a maximum and a minimum value inversely with the percent conduction time of said regulator;
(b) means for establishing a second current limit value which varies between a maximum and a minimum value as an inverse function of the time that the motor current is maintained at the lesser of said first current limit value or such second current limit value;
(c) means for comparing the current command signal value to the first and second current limit values and for producing said current reference value such that it acquires a value representative of the lesser of said current command signal value, said first current limit value, or said second current limit value;
and
(d) means for applying the current reference value to control the percent conduction time of the power regulator in a manner to minimize any difference between actual motor current magnitude and the magnitude of motor current corresponding to the acquired value of said current reference.

2 more elements

Dependencies are inferred from the claim text.