CIRCUITRY INNOVATION FOR THREE-PHASE MOTOR OPERATION ON SINGLE-PHASE POWER

Abstract

Power companies restrict the largest single-phase motors that they permit on their single-phase power distribution lines because of the high starting current of ordinary single-phase motors. These ordinary single-phase motors have low efficiency and power companies routinely restrict motor power to 7.5 horsepower (hp) or less without special permission. The operation of higher-power three-phase motors connected to a single-phase line have been previously inconvenienced by the need of a phase converter. This need has been overcome by the use of an Enabler™ circuit that connects the three-phase motor to the single-phase line. High-efficiency three-phase motors of 10 hp and 40 hp have now been running for several years on single-phase distribution lines. The starting currents are low and acceptable for the single-phase distribution lines. The running currents are high power-factor. The currents are balanced in the windings of these three-phase motors connected to the single-phase lines by capacitors in the Enabler circuit. Motor performance has been reliable.