GB272948A - Improvements in and relating to regulators for electric motors - Google Patents

Abstract

272,948. British Thomson-Houston Co., Ltd., (Assignees of Jump, G. H.). June 21, 1926, [Convention date]. Systems for alternating-current motors only; electric braking; controllers, liquid.-Liquid resistance apparatus varying t.he slip of an induction motor automatically according to the load is controlled so as to move automatically to a highresistance position before the motor is switched on to the supply. When the motor is adapted to run as a braking generator by reversing the connections or by changing over to a direct-current supply, the invention ensures that the change cannot be made until the slip-regulator is in a high-resistance position. In the arrangement shown in the Figure, the liquid resistance 13 connected to the rotor circuit of the induction motor 10 is varied automatically by a torque motor 19 energized from a series transformer 20. The apparatus is moved to the full-resistance position, as soon as the motor stator switch 23 is opened, by the automatic lowering of an extra counterweight 29 actuated through a worm drive by an auxiliary motor 32, the lowering action of this motor being determined by auxiliary contacts 42 associated with the stator switch 23. After the main motor has started.. the extra counterweight is raised by reversal of the auxiliary motor through a second pair of auxiliary contacts 37, and the resistance apparatus is left nearly balanced by the permanent counterweight 16 so as to be under the control of the torque motor. For electric braking a switch 24 changes over the stator connections to a direct-current supply 25; relays and electrical interlocks are disposed so that the auxiliary motor and extra. counterweight come into action as described above to put in full resistance before the change-over.