GB191412941A - Improvements in and relating to Motor Control Systems. - Google Patents

Abstract

12,941. British Thomson-Houston Co., [General Electric Co.]. May 2G. Systems for controlling reciprocating motion for planing-machines; electric braking.-Reversible motors, for example for planers, are braked with a larger initial resistance after the high-speed return than after the slow cutting stroke. This is effected by means of relays 25, 27, the latter comprising coils 28, 29 connected across the line and armature respectively. After the cutting stroke, using part of the resistance r in the circuit of the field F, the coils 28, 29 assist one another, the contactor B closing a local circuit through the resistance BR and only that part of B<1>R<1> not shorted by the contactor of the relay 27. After the quick return, the polarity of the armature running as a braking-generator is reversed, and, the coils 28, 29 being in opposition, braking is begun with the relay de-energized, thus placing all the resistance B<1>R<1> in circuit. As the back electromotive force of the armature decreases, the line coil preponderates, pulling up the contactor and cutting out a large step of the resistance. The relay 25 is used in connexion with starting-relays C, C' and reversing-relays R, R, which, with their interlccking mechanism and the brake relay B, are similar to those described in Specification 16,806/12. The present system comprises a switch T which controls leads running either to the 'automatic tappet controller S on the planer bed or to inching pushes 30, 31, and also simultaneously a motor voltage coil 12 controlling a series starting resistance D. The coil of the relay 25 is in two opposing parts, one of which is separately energized to close the contactor when the coil 12, in closing its contactor, has opened a switch 16. This opens the interlock 26 which removes a resistance 24 from parallel relationship with the starting or reversing coils, allowing them to become operative. Subsequent energization of the coil 12 as the armature speeds up opens the switch 16, current being then supplied to the field F through a wire 35 and one or both rheostats according to the stroke. The whole of the relay coil 25 is included in this circuit, causing the contactor to fall and prepare the resistance BR for inclusion in the braking-circuit.