Abstract: A propulsion system for traction vehicles utilizing separately excited electric traction motors in which a level of reverse motor torque is produced when speed control is released to effect a dynamic drag on the vehicle. The system simulates in an electric vehicle the dynamic drag effect characteristic of an internal combustion engine driven vehicle when the accelerator is released. The effect is attained by providing a motor armature regenerative current path through a load resistor and by maintaining motor field current at a selected minimum level when the speed control is released. A function generator adapted to regulate motor field current as a function of motor armature current provides a minimum field current signal when armature current is less than a selected value to thereby maintain field current and motor torque when the speed control is released.

Abstract: An electrical propulsion control system for self-propelled earthmoving traction vehicles of the type having integral earthmoving means and having a prime mover-driven electric generator supplying energy to traction motors, wherein the electrical output of the generator is regulated within predetermined maximum limits which are reduced in response to the application of a predetermined lifting force to the earthmoving means.

Abstract: An electrical propulsion control system for self-propelled traction vehicles having an electric generator supplying energy to separately excited traction motors, each motor field being normally excited with a substantially constant field excitation providing magnetic saturation such that motor load variations produce minimal changes in back emf, and means for equally boosting the excitation of each motor field responsive to the largest one of the individual motor armature currents exceeding a predetermined magnitude which is greater than the maximum attainable armature current during dynamic retarding operation.

Abstract: An electrical propulsion control system for self-propelled traction vehicles of the type having a prime mover-driven electric generator supplying energy to traction motors and regulating means for maintaining the electrical output of the generator within desired limits, wherein the limit of generator output voltage is varied between zero and a predetermined maximum level as a function of desired vehicle speed.

Abstract: An electrical propulsion control system for self-propelled traction vehicles of the type having a thermal prime mover-driven electric generator supplying energy to traction motors, wherein the electrical output of the generator is regulated within predetermined maximum voltage, current, and power limits and is independently reduced, without reducing the voltage or current limit, in response to the prime mover decelerating to speeds at which it is subject to bogging.

Abstract: In an electric propulsion control system for self-propelled traction vehicles having reversible, variable speed tractiOn motors, wherein the operation of a direction selector means overrides the normal speed controlling means and initiates a dynamic retardation operating mode so as automatically to decrease the speed of the traction motors, and means responsive to the motors subsequently decelerating to a predetermined relatively slow speed effects a reversal of motor energization so as to reverse the direction of the vehicle.