GB440498A - Improvements in systems for automatically controlling the speed of electric motor driven hoists and the like - Google Patents

Abstract

440,498. Automatic control of speed ; master control of A.C. motors. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. July 13, 1934, No. 20605. Convention date, July 20, 1933. [Class 38 (iv)] [See also Group XXXVII] A hoist motor or the like is so controlled that a mine cage, for example, may be brought to rest with a predetermined rate of deceleration. A generator 34 coupled to the hoist motor 13 produces a voltage, varying with the speed of the motor which is applied to a torque relay 37 controlling the direct or reversed application of power to the motor, but this voltage is modified in accordance with the position of the cage, when within the landing zone, by a resistance 35, in series with the relay, which is varied by fleeting gearing 42, coupled to the winding drum. A snap switch 71 in the relay circuit is operated by the resistance controller, so that the relay circuit is opened from the time the cage is brought to rest until it has left the landing zone. In operation the relay is held against chattering by a magnet 46 when the cage speed is correct, but upon divergence in speed it selectively closes the circuits of relays 60, 75, which energize contactors 16 or 17 to connect the hoist motor to apply driving or plugging torque to the winding drum as required to correct the divergence in speed. Specification 295,650, [Class 38 (iii)], is referred to.