GB588209A - Improvements relating to electric control systems for electric motors, steam engines and other prime movers - Google Patents

Abstract

588,209. Automatic control systems for winding gear &c. BRITISH THOMSON-HOUSTON CO., Ltd., and PETCH, T. H. Feb. 5, 1945, No. 2888. [Class 38 (iv)] [Also in Group XXXVII] Speed.-An electric motor, steam engine, or other prime mover, particularly one driving a lift or hoist, has a master controller and an auxiliary controller automatically maintaining the speed of the prime mover at that set by the master controller, and actuated by an electric motor fed from an auxiliary generator, the excitation of which is responsive to the setting of the master controller and to a tachometer generator driven by the prime mover. The auxiliary generator is preferably an amplidyne A of the kind described in Specification 539,835, the output of which is controlled by two main fields, one 5, 'excited through the master controller M.C. at a constant value, but reversible according to the direction of rotation selected, and the other 4, excited by a tachometer generator T.G. in series with a resistance R varied by the master controller, which may be of the type described in Specification 494,900, [Group XXXVII]. Should the prime mover not run at the speed set by the master controller, the differential excitation of the amplidyne will cause the auxiliary motor M. to operate correcting means. As shown in Fig. 1, this comprises resistance L.C. in the rotor circuit of an induction motor I.M., constituting the controlled prime mover and also a dynamic braking contactor D1, which introduces on negative loads (i.e. a load assisting the motor torque) braking by D.C. excitation or by a kind of low-frequency A.C., as described in Specification 516,666, [Group XXXVII]. Sets of contacts 16, 17 and 25, 26, in the master controller and the auxiliary controller ensure return of the latter to a neutral position after the motor has stopped and the control lever has been returned to neutral. Overload and anti-hunt fields 6, 7, are provided on the amplidyne. The auxiliary controller may actuate means for controlling prime movers other than electric motors by some form of directional and braking control: the resistance L.C., for example, may be replaced by a throttle control.