GB190903533A - Improvements in Control Systems for Electric Motors. - Google Patents

Abstract

3533. Peck, J. S. Feb. 12. Master control systems.-In a control system, the various connexions are made by electro-magnetic switches, with mechanism between the armatures and the switch arms to maintain the switches in position when they have been operated by the closing or opening coils. Two single-phase commutator motors 7, 8 are shown supplied from a line 27 through an auto-transformer, and switches 1 ... 6 make the circuits of different leads to vary the voltage of the motors. The switches 1 ... 6 are preferably of the known toggle type, and are provided with closing-coils 21 ... 26 and opening-coils 11 ... 16. Each of these switches also operates three auxiliary switches interlocked with other auxiliary switches. The connexions are arranged so that two switches are closed to connect a preventive resistance 47 across two points on the transformer. The middle point of the resistance 47 is connected to the motor circuit. A reversing switch 58 is operated by electro-magnets 50, 57. The coil 39 of a limit switch 38 is connected in the transformer circuit, and a circuit-breaker 30 is provided with a holding- coil 69 and a resetting-coil 40, energized from a point 90 on the auxiliary auto-transformer 70. In the "off" position of the controller 29, a circuit is completed from the auxiliary transformer 70 through the resetting-coil 40, conductor 138, and contacts 97, 68, 99 to earth. The circuit-breaker is operated to connect the transformer to the line 27. The reverser controller 78 is moved to complete the circuit of one of the electro-magnets 50, 57 to operate the reversing switch 58. When the controller is in the position a, a current flows from the conductor 100, through contacts 101, 59, 71, conductor 61, closing-coil 21, and interlocking switches 31, 43, 45 to earth. A similar circuit is completed through the closing-coil 22 and interlocking switches 32, 44, 46. The switches 1, 2 are then closed and the leads 106, 105 of the transformer are connected to the resistance 47, so that a voltage intermediate the voltage of these leads is impressed on the conductor 107 and on the motors. In the next position of the controller, the switches 2, 3 are closed, and the resistance 47 is connected to the leads 106, 112 of the transformer. Further movement of the controller causes the remaining switches to operate to increase the voltage supplied to the motors. If the line voltage fails or if an overload occurs, the circuit-breaker 30 moves to its open position and the auxiliary transformer supplies current to the opening-coils of the switches during the return movement of the controller. In a modification, the circuits of the operating-coils for the switches 1 ... 6 are controlled by relays operated by current from a battery or other source. The circuit-breaker can be connected on the low-tension side of the transformer, and the operating-coil of the limit switch is supplied from a series transformer. The arrangement of switches described may be employed in direct or alternating- current systems; and in the latter systems the switch-actuating coils may be supplied from a low-voltage point on the main transformer, or from an auxiliary transformer.