ELECTRIC MOTOR PROTECTIVE DEVICE Russian patent published in 1997 - IPC

FIELD: electrical engineering; overload and phase-failure protection of motors, especially those used in agriculture where operating conditions are far from being those specified. SUBSTANCE: winding 11, 12, 13, cores 1,2,3, and fuses 7,8,9 form three series circuits through which motor 15 is connected to supply mains phase leads; cores are built up of fixed and moving parts made of U-shaped strip material and separated by air gap formed by reset spring mounted on moving part of core; phase A winding 11 is placed on phase B core 2,5; phase B winding 12, on phase C core 2,6, and phase C winding 13, on phase A core 1,4; three-phase toggle switch 10 has three positions: START, RUN, and OFF; it is connected so that in START position it closes series circuits of fuses and split cores of respective phases until motor gains speed and then automatically changes over to RUN position (neutral position); in OFF position it closes leads of each of three windings thereby de-energizing the motor. EFFECT: improved reliability of protective gear. 1 dwg