GB612177A - Improvements in or relating to braking systems for induction motors - Google Patents

Abstract

612,177. Control of A.C. motors. IGRANIC ELECTRIC CO., Ltd. May 16, 1946, No. 14815. Convention date, May 24, 1945. [Class 38 (iii)] Non-regenerative braking.-A direct-current generator G is mechanically coupled to an induction motor 1, which may drive a hoist, and is adapted to be connected to the primary winding thereof during non - regenerative dynamo - electric braking, and alternating- current, induced in the motor secondary winding during braking, is rectified and is fed back to the primary winding so as to supplement the direct-current supply from said generator. At the first step of lowering an overhauling load, a master controller, not shown, is moved to energize a relay BR and remove a mechanical brake, thereby allowing the load to drive the rotor of the induction motor and the armature of the generator G. A main switch M, a hoist switch H and a switch D are de-energized, contacts H1 and D1 of the latter switches being closed to connect the generator G across one phase of the motor primary winding. A switch FB is closed to connect the motor secondary circuit to the primary circuit through half-wave rectifiers 4, 5 and 6 and rotor resistances R. A reactor 12 is provided to afford protection against possible flow of alternating-current due to arcing at certain switch-contacts. In a modification, full-wave rectification is provided instead of the halfwave rectification afforded by the rectifiers 4, 5 and 6. The rectifiers are preferably of the electronic type, for example argon-filled diode valves. Specification 596,157 is referred to.