Abstract: For a traction vehicle having two wheels driven by separate electric motors, a spin/stall condition is indicated if one of the wheels is rotating faster than a predetermined reference speed while the other wheel is not rotating, and a total stall condition is indicated if neither wheel is rotating and the magnitude of motor current exceeds a predetermined high level. Correction of any spin/stall condition is attempted by temporarily connecting a power resistor across the motor driving the spinning wheel, whereupon current (and hence torque) in the motor driving the stalled wheel will increase. Once a total stall is indicated, it is allowed to continue for a maximum period of time that varies inversely with the motor current magnitude, and if such condition is not earlier corrected motor damage is avoided by deenergizing both motors on the expiration of this period.

Abstract: Method and apparatus for optimizing power delivered by a prime mover-driven electric power alternator to an adjustable speed electric traction motor during high speed operation. The alternator is suitably controlled to deliver constant power if its output voltage does not exceed a first predetermined magnitude corresponding to a "corner point" speed of the motor and to limit the voltage magnitude when motor speed exceeds this corner point, thereby preventing excitation current from exceeding the maximum continuous field current rating of the alternator. As motor speed increases above corner point speed, less power is delivered to the motor, but the power reduction is minimized by increasing the voltage limit above the first predetermined magnitude. The amount of voltage limit increases, up to a predetermined maximum amount, is proportional to the amount load current in the motor decreases below its magnitude when motor speed equals corner point speed.