GB656762A - Improvements in or relating to electric motor controllers - Google Patents

Abstract

656,762. Controllers. WEST & CO., Ltd., A:. SMITH, M. A. CLEMENT-, and COUPAR, J. Dec. 2, 1948, No. 31246. [Class 38(iii)] Relates to means for preventing a too rapid acceleration of an electric motor. A master controller 2 for a series motor 1 is movable by means of a pedal 3 through a yieldable transmission device comprising a spring 4a. The movement of the controller is retarded by an eddy-current brake comprising a disc 5 and a coil 6 which is energized in accordance with the motor-current. If the retarding-force exerted by the disc 5 is small, the movement of the controller will closely follow that of the pedal, the spring 4a acting substantially as a solid coupling. If the braking-force increases, however, the spring will yield and continued movement of the pedal will have little effect upon the advancement of the controller. At a predetermined current a coil 8a closes contacts 8b to short-circuit an adjustable resister 7 in series with the coil 6. A ratchet device 9 allows the controller to rotate freely in the decelerating direction without moving the disc 5; the position of which may be adjustable relative to the magnetic field. The Provisional Specification refers to the provision of more than one current limit relay, means for entirely stopping the master controller when the motor current exceeds a given value, and energizing the brake coil from a constant voltage supply.