Abstract An apparatus for controlling the supply of power to an electric drive motor normally controls the duty cycle of a power switching element to produce a variety of vehicle speeds. The apparatus typically controls the rate of change of the duty cycle to provide smooth vehicle operation. During periods of extended high speed, high load operation the apparatus bypasses the power switching element and connects the vehicle battery directly to the drive motor via a contactor. Under normal operating conditions the bypass contactor is energized after a relatively short preselected delay; however, where the vehicle is heavily loaded, such that current limiting of the power switching element exists, the apparatus interactively delays energization of the bypass contactor to allow the vehicle sufficient time to accelerate to a higher speed. Such a control system advantageously reduces drive line shock and jerky operation of the vehicle, as well as, excessive sparking at the contactor.
An apparatus for selectively bypassing a power switching element of an electric vehicle drive system to continuously energize an electric motor of the vehicle drive system, the apparatus comprising: a bypass contactor connected in parallel with the power switching element; means for delivering a signal having a magnitude correlative to a desired duty cycle of the power switching element; means for detecting motor current; means for delivering a current limit signal in response to the detected current being greater than a preselected setpoint; means for receiving the desired duty cycle signal, comparing the desired duty cycle signal to a maximum duty cycle signal, and closing the bypass contactor a preselected duration of time after receiving the desired duty cycle signal having a value equal to the maximum duty cycle signal; means for altering the preselected duration of time in response to receiving the current limit signal.
Claim 2
Independent Claim
146 words
An apparatus for selectively bypassing a power switching element of an electric vehicle drive system to continuously energize an electric motor of the vehicle drive system, the apparatus comprising: a bypass contactor connected in parallel with the power switching element; means for delivering a signal having a magnitude correlative to a desired duty cycle of the power switching element; means for detecting motor current; means for delivering a current limit signal in response to the detected current being greater than a preselected setpoint; means for receiving the desired duty cycle signal, comparing the desired duty cycle signal to a maximum duty cycle signal, and closing the bypass contactor a preselected duration of time after receiving the desired duty cycle signal having a value equal to the maximum duty cycle signal; means for altering the preselected duration of time in response to receiving the current limit signal.
Claim 3
Dependent Claim
63 words
An apparatus, as set forth in claim 1, including: means for controlling the direction of energization of the motor; means for detecting the direction of energization, means for setting the preselected duration of time to a first value in response to the motor being energized for forward rotation, and to a second value in response to the motor being energized for reverse rotation.
Claim 4
Dependent Claim
31 words
An apparatus, as set forth in claim 2, wherein the means for setting the preselected duration of time sets the second value to a magnitude substantially greater than the first value.
Claim 5
Dependent Claim
26 words
An apparatus, as set forth in claim 1 wherein the altering means increases the preselected duration of time in response to receiving the current limit signal.