ELECTRIC MOTOR MONITORING CIRCUIT AND METHOD

摘要

An electric motor monitoring circuit apparatus (10) has a three phase electric motor (11) having an electric motor starter circuit. An insulation monitoring circuit (14) is coupled to the electric motor (11) and monitors insulation leakage of the motor (11). The insulation monitoring circuit (14) has a single phase AC power supply (36) for activating the starter circuit. A three phase monitor circuit (25) is coupled to the motor (11) for monitoring phase sequence in voltage amplitude for the motor (11). A relay circuit (22) inhibits activation of the motor upon detection of incorrect phasing or voltage or when insulation leakage exceeds a preselected threshold. The insulation monitoring circuit (14) closes a set of contacts to provide a ground return for the start circuit when the insulation monitor has determined the motor has passed the insulation monitor's test.