GB365244A - Improvements in or relating to control systems for electric motors - Google Patents

Abstract

365,244. Master control of D.C. motors; maintaining defined speeds. WESTING- HOUSE ELECTRIC & MANUFACTURING CO., East Pittsburg, U.S.A.-(Assignees of Dunlop, J. ; Park Ridge, Illinois, U.S.A.) Nov. 13, 1930, No. 34238. Convention date, Nov. 13, 1929. [Class 38 (iii).] Travelling between predetermined limits.-The speed of an elevator motor EM is made to obey a predetermined law during acceleration and retardation, by means of a regulator comprising two elements 9 and 7 which move according to the actual and desired rates of change of speed respectively, the element 7 being controlled by means operable in accordance with the position of the elevator with respect to a floor landing. To accelerate the elevator a master switch CS is moved to one of its extreme positions whereupon one of two direction switches 1, 2 is closed, and a resistance 84 in the field circuit of a Ward Leonard generator G supplying the motor EM, is cut out in two steps by relays 3, 4. Detents 69 and 120 are withdrawn from a cam disc 25 so that a spring 89 rotates the cam to give the element 7 a motion corresponding to a desired acceleration. The element 9 is moved in accordance with the actual acceleration by a centrifugal device 11, 12 mechanically connected with the elevator, and any difference between the two accelerations regulates the field of the generator G by means of a resistance 8, to reduce the difference. If it is desired to accelerate to an intermediate speed, the switch CS is given only a partial movement when only part of the resistance 84 is removed, and the detent 120 stops the cam 25 at a position corresponding to the intermediate speed. To stop the elevator the switch CS is brought to its central position,rand hatchway inductor relays 1LU, 2LU, or 1LD, 2LD and SR are actuated in turn to de-energize the relays 3, 4, open the direction switch 1 or 2, and apply a mechanical brake. A motor CM which is switched on when either of the relays 3, 4 is opened, rotates the cam disc 25 against its spring 89, to ensure that the deceleration takes place according to the predetermined law. Voltage relays 5, 6 are provided which open the circuit of the motor CM when the generator voltage reaches a low value, the contacts of these relays 5, 6 being closed when the voltage of the generator corresponds to values of the motor speed slightly lower than the intermediate, and the top speeds respectively.