Patent GB-461206-A (GB)
Title: Improvements in and relating to electric control systems employing electrically operated speed controllers
IPC: H02P5/50
Filed: 1935-10-26
Abstract: 461,206. Master control of two motors. BRITISH THOMSON-HOUSTON CO., Ltd. Oct. 26, 1935, No. 29611. Convention date, Oct. 27, 1934. [Class 38 (iii)] A control system for a plurality of driving motors 14, 15, comprises an electricallyoperated speed controller 24, 25, for each motor arranged to operate in steps, a common control circuit 22, 23, for the speed controllers reversely arranged rectifiers 44, 45, adapted to be selectively connected in the control circuit at the control station for selectively directing current through the control circuit, means in the circuit for controlling the operation of a remote speed controller to increase or decrease the speed of the associated driving motor depending on the direction of the current in the control circuit, and interlock means in the control circuit for causing the controllers to operate in step with each other. The invention may be applied to motors 14, 15, driving a tramway cable 10 utilized for laying the cables of a suspension bridge. Upon closure of a switch 52 a relay 56 is energized over contacts 43a of a master switch 43, and upon operation of the switch 43 to its forward position a circuit is completed over a control wire 21 for a relay 61 and a forward relay 41 for the motor 15. The circuit includes rectifiers 36, 39, which are connected to conduct current in the same direction. A rectifier 40 conducting current in the opposite direction prevents the energization of a reverse relay 42 under these conditions. The relay 61 completes a holding circuit for the relay 56, and energizes a forward contactor 17 for the motor 14, while the relay 41 energizes a forward contactor 19 for the motor 15. Thus the motors 14, 15, are connected for slow speed forward operation. Similar control for the reverse operation of the motors is effected over the wire 21 by operation of the switch 43 to its reverse position, the rectifiers 37 and 40 then conducting current to energize a reverse relay 42. Switches 64, 67, closed only in the full resistance positions of the resistance controllers 24, 25, of the main motors ensure that the motors 14, 15, can only be started from their lowest speed positions. To increase the speed of the motors 14, 15, a master switch 76 is moved to a " fast " position whereby an energizing circuit is completed for a fast relay 48 for the motor 15, and a relay 80 is simultaneously energized to close a circuit for a fast relay 77 for the motor 14. The circuit for the relay 48 is complete over control wires 22, 23, through rectifiers 44, 46, which are so connected as to conduct current in the same direction, a rectifier 47 in the circuit of a " slow relay 49 being connected to prevent a flow of current with these connections. With relays 48, and 77 closed, contactors 31 and 34 are energized so that pilot motors 30, 33, operating the controllers 24, 25, respectively, are connected to operate in a speed increasing direction. Similar control for " slow " operation of the motors 30, 33, to decrease the speeds of the motors 14, 15, is effected over the wires 22, 23, by operating the switch 76 to its " slow " position ; the rectifiers 45, 47, then conducting current to energize the " slow " relay 49. If one of the controllers 24, 25, say 25, moves faster than the other, a positioning relay 51 is energized over contacts 25b of the controller 25, and completes a holding circuit for the contactor 34, and interrupts the circuit of the " fast " relay 48. Thus the control of the contactor 34 is transferred from the " fast " relay 48 to the controller 25 and the relay 51. The relay 80 is also de-energized, so that when the controller 24 completes a circuit for a positioning relay 50 over its contacts 24b, this relay 50 similarly transfers the control of the contactor 31 from the " fast " relay 77 to the controller 24 and the relay 50. When the controller 25 completes a step movement its contacts 25b de-energize the relay 51 which opens to de-energize the contactor 34, and so the controller 25 is stopped, and similarly the controller 24 is stopped when it has completed the corresponding step. The de-energization of the relay 50 which results when the controller 24 completes its step re-energizes the relay 90 and the relays 48, 77, again respond and the controllers 24, 25, are moved another step. A similar control is effected for each step. When the motors 14, 15 are operating at the desired speed, the switch 76 is returned to its off position to de-energize the relay 80 which causes the pilot motors to stop. When the motors 14, 15, are disconnected the pilot motors 30, 33, are energized in response to the closure of back contacts on the contactors 17-20 to return the controllers 24, 25, to their initial positions. Indicating lamps 95, 96 are provided to show that the controllers 24, 25, are operating properly, and limit switches 63, 66, are operated when the driving motors 14, 15, reach their limits. Switches 24a, 25a serve for stopping the pilot motors 30, 33, when they reach their final positions. Push-button switches 78, 83, enable either of the controllers 24, 25, to be operated independently.