Prime mover speed responsive load control for electrically propelled traction vehicles

Claim 1

For use in a traction vehicle including electric traction motor means for propelling the vehicle, electrical generating means for supplying electrical energy to said motor means, and thermal prime mover means for driving said generating means at a speed which normally is relatively constant, said prime mover also being adapted to supply power for additional auxiliary loads, an electric propulsion control system adapted to regulate the electrical output of said generating means within given limits and to control the performance of said motor means, said control system comprising: a. a variable excitation source arranged normally to supply a predetermined maximum level of excitation to the field of said generating means; b. first means for providing feedback signals which vary as functions of voltage and current levels of the electrical output supplied by said generating means to said motor means; c. second means for providing reference signals representative of desired performance limits of said motor means; d. comparison means responsive to said feedback and reference signals for generating error signals indicative of the actual performance of said motor means exceeding said limits; e. load control means responsive solely to the shaft speed of said prime mover means for producing a load control signal indicative of said shaft speed decreasing to angular velocities at which said prime mover means is subject to bogging as a result of excessive load demand; and f. means associated with said excitation source for modifying the excitation of said generating means as a function of said error signals and independently as a function of said load control signal.