Three wire power supply circuit

Abstract

A power supply circuit is provided for use in combination with a load and an alternating current (AC) power source for selectively connecting and disconnecting the load and the AC power source. The load is connected between a neutral conductor of the AC power source and the power supply circuit. The power supply circuit is connected to a power or hot line conductor and a ground conductor of the AC power source. The power supply circuit comprises relay connected in series between the load and the line conductor; a control circuit for selectively operating the relay; and a transformer. The primary winding of the transformer is connected in series with the line conductor and the ground conductor for supplying power to the control circuit even when the load is disconnected from the AC power source. The power supply circuit comprises a switch in series with the primary winding of the potential transformer for interrupting the primary winding current at frequencies above the AC line frequency. The power supply circuit can also comprise a slide or air gap switch to isolate the power supply circuit from the AC power source when the air gap switch is in the OFF position or to limit current to an acceptable level. The air gap switch can be configured to pulse the primary winding current above the accepted level.

Dependencies are inferred from the claim text.