GB523034A - Improvements in or relating to electric elevator control systems - Google Patents

Abstract

523,034. Master control of A.C. motors. WESTINGHOUSE ELECTRIC & MANUFACTURING CO. Dec. 22, 1938, No. 37338. Convention date, Dec. 23, 1937. [Class 38 (iii)] [Also in Group XXXV] An electric elevator control system comprises a motor H driving a car 10, the speed of the car being controlled by an eddy current brake B controlled by the output of an auxiliary speeddetermining generator S. A stopping brake 17 of the electromagnetic type may be provided. Movement of car switch CS to its high-speed position energizes up-contactor coil U or downcontactor coil D and conditioning relay M if the gate and door contacts 47, 48 are closed. Relay M connects the constant-speed motor 41 to drive the regulating generator 36, the regulating field RF2 of which is connected to generator S. The hoisting motor H starts and rotor resistances are cut out gradually by time delay contactors. During such high-speed operation brake B is deenergized, its constant field stator winding BF4 and its regulating stator winding BF5 being disconnected by relay P. When the car is to be stopped switch CS is moved back one notch to de-energize P and connect the eddy current brake fields BF4, BF5. Field BF5 is supplied from generator 36 to obtain a constant car speed, say 130 feet per minute. The constant field RF1 of generator 36 is supplied through part of resistance rll and is opposed by the regulating field RF2 energized in accordance with speed by auxiliary generator S. A third field RF6 connected in series with the armature 36 may be provided. Field BF5 opposes or assists BF4 according as the car speed varies from the required speed. Energization of coil P also effects energization of limit relay coil T to reinsert the rotor resistances of the motor H. With full load in the lift car the insertion of these resistors may be arranged to bring the car to the required speed without use of the brake B, the fields BF4, BF5 of which are then equally and oppositely energized. When the car is to be stopped the switch CS is moved back to notch 50 and the whole of resistance rll is inserted in the circuit of field RF1 when the brake B causes decrease of the car speed to say 30 feet per minute. The torque output of the motor increases with falling speed and a balance may be arranged to occur at 30 feet per minute. The lift is stopped by centreing switch CS so that the system is de-energized and brake 17 is applied.