GB552886A - Improvements in and relating to electric motor control systems - Google Patents

Abstract

552,886. Master control of D.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd. July 24, 1941, No. 9394. Convention date, July 24, 1940. [Class 38 (iii)] Multiple unit control is arranged so that when the controller D on the leading vehicle is placed in its " coasting position, all motors are connected in braking loops, and when the controller D is in a motoring position, none of the units can start motoring unless the braking loops of all units are opened and unless all units are connected for the same direction of movement. During operation, switch 124 is closed on to contact 138. Field reversing switches are associated with a drum switch R, and only when drum R corresponds in position with a selector switch S, and when a braking contactor B has dropped out, is a circuit completed over S, R, and contacts 98 on B for a correct order relay COR. When all the relays COR of the various units close their contacts 99 in series in a train wire, then a relay CR on the driving unit lifts and permits the controller D to energize a train wire 12 to which is connected on each unit the operating coils 144 of a line breaker LB1 ; this circuit is over contacts 145 of a contactor LC normally always up and contacts 146 of a potential relay PR energized from trolley 40. Before relay COR lifts, its contacts 131 energize a lifting coil 130 of an indicating relay IR which lights an indicating lamp 134 and holds up on coil 133 until line breaker LB1 lifts. If the relay COR of any unit fails to lift, momentary depression of button 140, with the controller D in a motoring or coasting position, causes coil 64 to lift the relay COR and latch it up and to open its contacts 94 and so cause the contactor LC to drop and open the circuit of the motors. Acceleration is effected by an oil motor KM, as in Specification 537,739, cutting out a resistor 39 from right to left whereupon a transfer switch TS lifts and the resistor 39 is again cut out from left to right, anally the fields of the motors are shunted. Motion of the oil motor KM is retarded by the action of a vibrating " acceleration and braking relay ABR. In the " full run " position of the controller D, the bias on the relay ABR is increased to give a greater acceleration. During coasting, a field flashing circuit, and a braking loop are completed by the lifting of contactor B and the motor KM adjusts the current in the loop to a low valve, as in Specifications 513,114 and 514,263. In a "braking" position of the controller D, a resistor 180 is inserted in circuit with the actuating coil of relay ABR, and motor KM adjust resistor 39 to pass a braking current. " Full braking " position of controller D increases the bias on the relay ABR. Whilst the speed is high on voltage limit relay VLR controls the oil motor KM. The various control circuits are supplied from a battery V, some through a latched switch CC, but the coil of contactor LC is direct on the battery, and in series with a resistor L to limit current drain on battery in the event of a short circuit.