Patent GB-635850-A (GB)
Title: A control system for electric traction motors
IPC: B60L7/04
Filed: 1947-08-28
Abstract: 635,850. Master control of D.C. motors. FORGES ET ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE JEUMONT. Aug. 28, 1947, No. 23821. Convention date, April 19, 1944. [Class 38 (iii)] In a control system for two electric traction motors or groups of motors interconnected by a circuit of the two-branch type and operated by a plurality of cam-contactors, the cam-contactors are grouped to be actuated by two separate cam-shafts, the first group being provided for effecting the series-parallel motoring connections, the field control in motoring and the crossed-field braking connection of the motors, while the second group is provided for controlling the starting and braking resistances, the two cam-shafts being adapted to effect all operations of the respective groups by combined and conjugate movements, in co-operation with an additional braking contactor arranged for increasing the number of braking positions,. and with a special field contactor providing a complementary field circuit in the braking operation. As shown, the equipment for a motor coach comprises motors A1, A2, having field windings B1, B2. A first controller regulates contact A-N, field-weakening contacts Q-W, and an additional braking contact P. A second controller operates contacts connected to sections of resistors R1, R2. The cam-shafts of the two controllers are driven by pilot motors. For motoring operation, the first controller moves from the " off " position to effect the connection of the traction motors in series. The second cam-shaft then moves gradually to short-circuit resistors R1, R2. The first controller then continues its movement to effect field-weakening. On the fifth notch of the first controller a transition connection of the working motors is made, the parallel connection being effected on the sixth notch, and thereafter the field-weakening contacts are again actuated. On the sixth notch of the first controller, the second cam-shaft effects a new rotation to remove resistors R1, R2. For braking operation, the first cam-shaft moves from the zero position to effect a crossed-field rheostatic braking connection, resistors R3, R4, being initially connected in series with resistors R1, R2, and being cut out on the second and third braking notches by contactors M, N. At the third braking notch, the second cam-shaft moves to short-circuit resitors R1, R2. Further movement of the first controller in the braking direction enables a reverser to be operated through a mechanical device. A contact P is closed on the fourth braking notch of the first cam-shaft, and the number of braking connections may be increased by alternately moving the first controller between the fourth and third braking positions, the second camshaft being stepped on one notch at each alternation. With low values of braking current, a separate field excitation may be provided through contact J, field winding B2, special contactor RC1 and resistor R5. A circuit-breaker DJ protects against accidental earthing, and over-loading during motoring operation. It stops cross-energization if there is a failure during parallel motoring operation.