GB598737A - Improvements in or relating to electric motor control systems - Google Patents

Abstract

598,737. Control of D.C. motors. IGRANIC ELECTRIC CO., Ltd. Sept. 7, 1945, No. 23123. Convention date, Sept. 8, 1944. [Class 38(iii)] Any desired control in accordance with the rate of deceleration of a motor is obtained by means of a charged condenser and a control winding connected across the armature of the motor so that the discharge rate of the condenser increases with the rate of deceleration of the motor. As shown an electromechanical brake B, for example of a D.C. hoist motor M, is controlled in accordance with the rate of deceleration of the motor during dynamic braking by charging a condenser C from the armature volts and permitting this condenser to discharge through the holding coil C1 of a relay DR as the motor slows up. When the rate of retardation is below a predetermined value, or when the motor comes substantially to rest, the current in this coil becomes insufficient to hold in the contact d of the relay DR and a relay BR, which keeps the release magnet of the brake B energised, then opens its contacts. The actuating winding c of the relay DR is shunted to delay opening until a relay DB has had time to close the dynamic braking circuit. Should the motor accelerate instead of slowing down a rectifier R ensures that the coil C1 is unexcited and the brake B will be immediately applied.