CONTROL UNIT FOR THREE-PHASE ASYNCHRONOUS MOTOR OPERATION Russian patent published in 2010 - IPC H02H7/09 

FIELD: electricity.

SUBSTANCE: voltage between zero points of mains and stator winding is increased when phase is lost. Voltage at diode bridge input is increased and intermediate relay (11) is actuated resulting in connection of the second starter coil (16) by relay contact (14) without thermal relay which interconnects zero points of stator windings and mains by its contact (17). As a result, the said thermal relay switches on signalling device (20) (for example, lamp indicator). Current having value equal to the current of each of two entire motor phases flows along zero mains wire through one of poles (19) of double-pole circuit breaker. If this current is less than actuation current, the motor continues its operation and signalling device (20) records loss of phase. If current is higher than the circuit breaker actuation current, double-pole circuit breaker will switch off in some time and switch off coil (3) of the first magnet starter by its contact (18), and contact (4) will breaker the circuit. The motor will be disconnected from the mains. If current is less than motor actuation current, the motor continues its operation providing for the possibility to personnel to take appropriate measures to eliminate accidents without any faults or interruptions in consumer operation.

EFFECT: reduced energy costs, fault-free operation and alarm in case of loss of phase and motor protection from overloading.

1 dwg