Patent GB-716559-A (GB)
Title: Improvements in and relating to remote control systems for electric motors
IPC: H02H7/00
Filed: 1952-09-11
Abstract: 716,559. Protective cut-out arrangements; controllers; control of several motors. BROOKE, W. Sept. 11, 1952 [Sept. 12, 1951], No. 21436/51. Classes 38(3) and 38(5) In an arrangement for the remote control and protection of a polyphase electric motor having a large capacity condenser C in parallel with the operating coil R1 of a remote control relay R, generally as described in Specification 669,607, a further large capacity condenser D is connected in series with the pilot circuit to provide an impulse to assist in closing the relay R. In Fig. 1 when the motor M is not running and the remote control switch H is in the " off " position H1, current initially flows from the secondary winding T2 of a transformer through the condenser C and coil R1 in parallel, through connection 15, switch F1. pilot wire 11, through rectifier K, switch H and earth conductor 10. The condenser D is charged and the flow of current in the control or pilot circuit ceases. When the switch H is moved into the " on " position the rectifier K is replaced by the reversely connected half-wave rectifier J so that on the appropriate half cycle current flows round the control circuit in the reverse direction and is initially supplemented by the discharge of the condenser D to provide a pulse which closes the relay R. Thereafter the half wave rectified current flowing in the control circuit is just sufficient to retain the relay closed. On the closing of the relay R, contacts R2 close the circuit L1, G, E, R2, G, L2 to energize the coil E of a contactor F which closes and starts the motor M, and contacts R3 short circuit the condenser D. Should a fault occur as failure of the supply or the open circuiting of the control circuit which opens the relay R and the switch H is left in the " on " position, the motor is not started automatically on the resumption of the supply as the half-wave current through the rectifier J can flow through a resistance B and rectifier A and the condenser D is not charged to provide a closing impulse. Re-starting is effected by moving the switch " off " and reclosing it. In a modified arrangement, Fig. 7, a single rectifier is used in conjunction with a remote reversing switch H. The switch comprises a sliding shuttle K1 with metal ends 33. 34 interconnected by a germanium diode rectifier, the ends co-operating with fixed contacts 30, 31, 32. Figs. 2 to 6 and 9 (not shown) illustrate other modifications of the control switch and associated rectifier or rectifiers. Fig. 8 shows the arrangement applied to the sequential control of a system of conveyers Q, QA, &c. With the switch H in the position shown, the condenser D in the first gate end box O is charged through a resistance P and a rectifier K. When the switch H is closed, the rectifier K is short circuited and current flows through the rectifier J to close the relay R and contactor F closes to start the motor M of the conveyer Q. Contacts F1 of the contactor F close to connect a rectifier KA in the control circuit of the second conveyer QA to charge the condenser DA in the second gate end box OA. When the first conveyer Q approaches full speed, a centrifugally operated belt switch V closes to short circuit the rectifier KA, whereupon current can flow through the rectifier JA associated with the second motor MA to close the relay RA. The second conveyer is now started and the sequence of operation proceeds until all the conveyers are running. In the event of a fault causing the opening of any relay and the stopping of the associated conveyer, the opening of the contacts F1 of the associated contactor causes in turn the stopping of all the conveyers behind the faulty conveyer so that " piling is prevented.