Power interruption protection system for electric motors

A power interruption protection system for AC electric motors. An electroresponsive relay (OL) in the energizing circuit of an electroresponsive main power contactor (MC) for an AC motor is responsive to deliberately deenergize the contactor if a power supply interruption persists for more than a few cycles of the supply frequency. A motor current level detector (CLD) monitors the motor current and if it falls below a predetermined level activates a pulse counter (CTR) to register pulses from a clock pulse generator (CPG) which produces pulses each half cycle of the supply frequency. If the pulse counter registers a certain number or more of such pulses an amplifier-driver (AD) energizes the relay to effect disconnection of the motor from the AC supply. The system is disclosed both as a stand-alone system, and as combined in a system affording current overload protection modes as well for AC motors.