Abstract: In an electrical propulsion system on board a moving traction vehicle (such as a rapid transit rail car) having current collectors in contact with an energized third rail, controllable switch means is used to connect the system to the current collectors. From time to time the current collectors traverse gaps between adjacent sections of the third rail, in which event regenerative braking operation of the system will be prevented unless the next third rail section is energized by a wayside source of voltage. The switch means comprises the parallel combination of a diode that conducts current when the system is operating in a motoring mode and a reversely-poled thyristor that conducts regenerative braking current once a firing signal is applied thereto.

Abstract: The magnitudes of currents in the armature and field windings of a separately excited d-c motor are compared, and a fault signal is produced in response to the field current magnitude either rising above a first reference level (which varies as a first predetermined function of the armature current magnitude) or falling below a second reference level (which varies as another predetermined function of the latter magnitude).

Abstract: Two separately-excited d-c electric motors are used to drive the wheels of a traction vehicle. The magnitude of motor field current varies as a function of the value of a variable control signal, which value is representative of any deviation of the field current magnitude from a given reference magnitude. When electric braking of the vehicle is desired, the reference magnitude is normally determined by the difference (if any) between the actual rotational speed of the slower motor and a predetermined desired speed, whereby motor field current is varied as necessary to regulate the retard speed of the vehicle. Means is provided for automatically initiating the retard speed regulation mode of operation as the vehicle accelerates and the actual rotational speed of the faster motor approaches the aforesaid desired speed.

Abstract: An improved automatic control system for a train of transit vehicles which regulates the velocity of the train and its braking rate in accordance with a predetermined velocity/distance profile. The system includes apparatus for compensating for variations in wheel diameter and train length in such a manner as to assure that the center of the train regularly stops at a predetermined point with respect to a desired station stopping point. On board receivers are responsive to wayside signal devices for establishing the operating velocity of the vehicle and for initiating entry into the predetermined braking profile. Since vehicle control is effected by wayside signal devices, the distance between stopping points may be indefinite. The system includes apparatus which permits passing selected stopping points when desired.

Abstract: A control system for a self-excited alternator which includes an auxiliary winding adapted to supply excitation to the alternator field winding incorporates a circuit for supplementing field excitation when the available energy from the auxiliary winding is less than the desired magnitude of field excitation. The self-exciting a-c current from the auxiliary winding is coupled through a phase-controlled rectifier circuit to the alternator field winding. A secondary excitation source such as a battery is coupled to the alternator field winding through a chopper circuit. A regulating circuit is responsive to a field current reference signal for controlling the conduction of the phase controlled rectifier circuit and the chopper circuit in a manner to regulate the alternator field excitation to the desired value.