GB463003A - Improvements in or relating to systems of control for electrically operated lifts - Google Patents

Abstract

463,003. Control of A.C. motors. GENERAL ELECTRIC CO., Ltd., and CHUBB, A. A. Dec. 6, 1935, No. 33830. [Class 38 (iii)] Non-regenerative braking. -For slowing down an asynchronous motor ST driving a lift, direct current derived from the supply through rectifiers YA, YB, is applied to its windings, the rectifiers being connected in parallel with resistances or impedances RA, RB. The invention is described in the case of the driving motor of a lift system operating as described in Specification 453,723, [Group XXVIII]. Upon operation'of a callbutton, a directional contactor UD or DD is closed and the lift is started and accelerated to full speed. As the lift approaches the floor to which it is called a relay DC is energized in response to the actuation of an inductor relay to open at contacts dc1, dc2, short-circuits across rectifiers YA, YB, connected in series with the driving motor stator windings. Thus, the motor is subjected to direct-current energization to an extent determined by adjustable resistances RA, RB. The lift is braked and as it approaches the desired floor, a relay, operating in response to the actuation of another inductor relay, de-energizes the directional contactor UD or DD. The driving motor is thus disconnected and a friction brake K applied. Where the lift system includes a switch positioned in accordance with the load on the driving motor as in the system described in Specification 454,725 contact banks provided on these switches may adjust the resistances RA, RB in parallel with the rectifiers YA, YB, in accordance with the load. Suitable resistances may be inserted in the rotor circuit for braking. Reference has been directed by the Comptroller to U.S.A. Specification 1,945,392.