ELECTRIC MOTOR PROTECTIVE DEVICE Russian patent published in 1998 - IPC

FIELD: electrical engineering; phase-failure and overcurrent protection of three-phase induction motors. SUBSTANCE: device has two separate channels one used for phase-failure protection and other channel, for overcurrent protection. Phase-failure protection channel has two series-connected threshold elements 18, 8 whose outputs are connected to time-setting circuits 5, 6. Input of first threshold element is connected to output of voltage sensor rectifier 4; output of second threshold element is connected through OR gate 14 to input of final element 15; overcurrent protection channel also has two series-connected threshold elements 12,13 whose outputs are connected to time-setting circuits 10, 11; inputs of first threshold element 12 and of second time-setting circuit 11 of this channel are connected to output of overcurrent sensor rectifier 9; input of second threshold element is connected through time-setting circuit to inverse-current circuit; output of second threshold element is connected through OR gate to output of final element 15. EFFECT: improved operating reliability. 1 dwg