THREE PHASE MOTOR CONVERSION AND MONITORING CIRCUIT

摘要

A three phase motor conversion and monitoring circuit converts a three phase motor to be started and run on single phase line power. During motor start-up, the circuit connects a start capacitor across a first input pair of the motor via a normally closed relay contact. The circuit includes a power supply connected across a first motor input pair which powers both a voltage monitor connected across a different input pair and a phase sequencing detector. When normal run voltage is detected across the first and second input pairs, and if and only if the phase sequencing detector has detected a normal phase sequence indicating that the motor is rotating in the correct direction, the relay is operated to open the normally closed contacts and to remove the start capacitor from the motor circuit.