Abstract: A control circuit for a d.c. motor for an electric vehicle operates by controlling motor current in accordance with the error between a current demand signal and a signal derived from a current transducer. The current demand signal is generated by a potentiometer array, with the potentiometer slider connected to an input terminal of an operation amplifier. This amplifier has its output terminal connected by a resistor to a capacitor connected by another resistor to the base of an emitter follower transistor. The emitter of this transistor is coupled by a feedback resistor to the inverting input terminal of the operational amplifier.

Abstract: An electric vehicle traction motor control circuit includes a main thyristor in series with a fuse, and the armature of the motor. A second thyristor and a commutating capacitor are connected in series across the series combination of the main thyristor and fuse. A third thyristor is connected in series with an inductor across the capacitor, and when fired, acts to reverse the voltage stored on the capacitor following commutation. The circuit is capable of operating in an emergency operating mode when the fuse is blown, by alternate firing of the second and third thyristors at a fixed frequency.

Abstract: An electric vehicle traction motor control circuit includes a main thyristor in series with the motor armature. A second thyristor is connected in series with a commutating capacitor across the main thyristor which can be switched off by firing the second thyristor so that the motor current is diverted into the commutating capacitor. A third thyristor is connected in series with an inductor across the commutating capacitor and serves when fired to reverse the voltage residing on the commutating capacitor following commutating. The reversed voltage on the capacitor is detected and is used to control upper and lower current limit signals set by a driver operable control so that the capacitor is not called upon to receive a large current when it is in a low voltage condition.

Abstract: An electric vehicle traction motor control circuit includes a main thyristor in series with the motor armature between two supply rails. A second thyristor is connected in series with a commutating capacitor across the main thyristor which it can turn off by diverting the motor current briefly into the commutating capacitor. A third thyristor is connected in series with an inductor across the commutating capacitor and serves when fired, to reverse the voltage residing on the commutating capacitor following commutation. The second thyristor is connected to a pulse generator which is connected to be edge-triggered by the output of a comparator comparing actual motor current with upper and lower current limits set by a driver operable control. The comparator also brings an oscillator into operation which provides additional trigger inputs to the pulse generator if the latter fails to be edge-triggered by the comparator output.

Abstract: An electric vehicle traction motor control circuit includes a main thyristor in series with the motor armature. A second thyristor is connected in series with a commutating capacitor across the main thyristor which can be turned off by firing the second thyristor to divert the motor current momentarily into the commutating capacitor. A third thyristor is connected in series with an inductor across the commutating capacitor and serves on firing to reverse the voltage residing on the commutating capacitor following commutation. A circuit is connected to detect the cessation of current flow into the commutating capacitor and acts to fire the third thyristor when such cessation is detected.