ELECTRIC MOTOR PROTECTION DEVICE Russian patent published in 1994 - IPC

FIELD: electric technique. SUBSTANCE: device has an actuator, thyristor, pulse generator on the basis of a unijunction transistor, comparator, measuring bridge with a temperature sensor at its input connected through a diode and resistor to one phase of the mains. The unijunction transistor is connected to the output of the comparator and its emitter is connected to RC-circuit connected to a second capacitor connected through a second diode to a another phase of the mains to a third phase of which through the thyristor the actuator is connected so as to simplify circuit and enhance operating reliability. Furthermore, the device provides protection of the electric motor from overheating, incomplete-phase operating mode, breaks and short circuiting in the temperature sensor circuit. EFFECT: widened operating capabilities, simplified construction and enhanced reliability. 4 cl, 1 dwg