GB322856A - Improvements in and relating to electric motor control - Google Patents

Abstract

322,856. British Thomson-Houston Co., Ltd., and Pool, W. J. Oct. 29, 1928. Speed maintaining systems. - Relates to a system of the kind described in Specification 205,215 for maintaining proportionate speeds of a number of electric motors by automatically shifting speed-controlling brushes through the agency of a synchronous-type dynamo-electric machine with a driven armature and a freely rotatable field, the machine serving as a regulating-motor. According to the invention the brushshifting gear can be unclutched from driving connection with the regulating-motor and can be clutched into driving connection with a separate small motor or other means for giving independent adjustment to the brushes. Fig. 1 shows one form of apparatus comprising a regulating motors 1 with its free member geared to a wheel 7 fitted with a clutch 8 transmitting motion to a brush-shifting shaft 9. The shaft 9 can be unclutched from the wheel 7 and clutched to a separate small motor 14 by the movement of a pivoted arm 17 linked to the core of a solenoid 19, and a free-wheel ratchet device 23, 24, Figs. 1 and 2, mounted on a quick-threaded screw 26, is arranged to actuate a change-over switch 29 in circuit with the solenoid 19 and with a fieldwinding of the motor 14. During normal working of the controlled motor (not shown), the shaft 9 remains coupled to the regulating-motor which receives three-phase current from a master alternator and has its armature driven through the belt 3. For starting-up or shutting-down the controlled-motor, the shaft 9 is temporarily coupled to the motor 14 by suitably arranging the circuits in connection with the above described apparatus. Specification 278,062 also is referred to.