GB115099A - Improvements in and relating to Systems of Electric Motor Control. - Google Patents

Abstract

115,099. British Thomson - Houston Co., (General Electric Co.). April 30, 1917. Systems for controlling reciprocating motion.- An electric motor for driving machine tools or performing similar work is reversed by means of electro-magnetic switches which are energized under manual control for closing circuit, but are de-energized automatically as the motor speed drops. The motor A with interpole windings F and shunt field winding F<1> is supplied from the mains L, L<1> through a controller C reversing- contactors B, D and a series resistance contactor 11. The contactors B, D are interlocked so as to prevent either from closing until the other has opened. In the forward position of the controller, the contacts engage along the lines b, b<1> and the actuating circuit of the contactor B is completed. The contactor closes and the motor circuit is then complete-through the controller C, contactor B, actuating coil of contactor 11 and resistance R. As the current drops, the contactor 11 closes to cut out the resistance R and also to open the switch 16, thereby inserting the resistance R<1> in the shunt field circuit. This resistance is then left in circuit subject to the usual action of a vibrating relay 18. During the running period, the actuating coil of contactor B is connected across the motor armature and is independent of the controller so that, when the controller is moved to the reverse position, the contactor B cannot open until the motor speed has dropped to a predetermined, value. The movement of the controller to the reverse position closes a dynamic braking circuit through the resistance B, R. A similar action occurs at the end of the reverse run with the contactor D closed.