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.

Abstract: A phase-controlled ac-to-dc rectifying circuit includes a pair of alternately conducting main controllable electric valves and cyclically operative forced commutation means for turning off the main valves. The forced commutation means comprises a pair of auxiliary controlled rectifiers respectively connected, in circuit with a commutating capacitor, across the main valves, and the auxiliary rectifiers are alternately turned on in response to periodic trigger signals that are normally produced by associated control means. Protective means is provided for inhibiting the trigger signals when the magnitude of voltage across the commutating capacitor is lower than a critical level which depends on the magnitude of the current being conducted by the main valves, thereby avoiding a risk of commutation failure due to low capacitor voltage.

Abstract: In the propulsion system of an electric locomotive, a-c wayside power is converted to direct current for the traction motors by means of several phase-controlled rectifying bridges having serially connected outputs. The bridges are controlled sequentially so that their respective output voltages are introduced in stages as increasing amounts of voltage are required at the motors of an accelerating locomotive. Normally certain thresholds of speed need to be attained before the second bridge, and later the third bridge, are permitted to be phased on. Means is provided for changing the bridge control sequence in response to faults in the first or second bridges.

Abstract: In the propulsion system of an electric locomotive, a-c wayside power is converted to direct current for the traction motors by a plurality of phase-controlled rectifying circuits having serially connected outputs. To improve power factor, forced commutation means is provided for turning off the controllable valves in one of the circuits at a desired "extinction angle." This angle is varied with motor speed, but its effective range of variation is restricted so as to avoid undesired leading power factor at low speeds, to optimize power factor when the locomotive is running at full power, and to prevent misoperation when the level of load current is low.

Abstract: A multi-axle traction vehicle is equipped with apparatus for sensing the speeds of its respective drive axles, and control apparatus is provided for producing a predetermined warning signal if the sensed speed of one and only one of the axles is less than a predetermined low threshold level. In addition, apparatus is provided for inhibiting the control apparatus unless all but one of the sensed axle speeds are greater than a predetermined higher threshold level thereby minimizing the opportunity of producing a false warning signal.