Zero current switching circuitry

Claim 1

A control circuit for controlled deenergization of an electromagnetic circuit breaker which interconnects an AC voltage source and a load such that said circuit breaker interconnection contacts open at a zero current point on said source output waveform comprising: An electromagnetic circuit breaker including coil energization state responsive contact interrupter means, said circuit breaker characterized by a determined time delay between time of deenergization of said contact interruptor means and time of circuit breaker interconnection contacts opening; sensing means for sensing the waveform of said load current; signal processing means coupled to the output of said sensing means including means for generating a square wave signal in phase with the waveform of said load current, and means for phase shifting said square wave signal, said phase shifting means adapted to permit shifting of the phase of said square wave signal an amount directly proportional to said predetermined time delay of said contact interrupter means of said circuit breaker; amplifier means for amplifying the output of said signal processing means, the output of said amplifier means being a square wave signal of selected amplitude; solid state switching means having a square wave signal conductive path, said switching means including DC voltage responsive trigger means, a DC voltage source, and means for applying said DC voltage source to said trigger means, said means for applying incorporating at least one disconnect means, said switching means adapted to interrupt said signal conductive path thereof at the next zero crossing of the square wave input signal thereto subsequent to disconnect of said DC voltage source from said trigger means, and cascade interconnection means adapted to interconnect said sensing means, said signal processing means, said amplifier means, said square wave signal conductive path of said solid state switching means and said contact interrupter means of said circuit breaker such that the output of said amplifier means energizes said contact interrupter means when said DC voltage source is connected to said trigger means of said switching means and such that energization of said contact interrupter means of said circuit breaker ceases a predetermined time in advance of the next to occur zero current point on said source output waveform when said DC voltage is disconnected from said trigger means of said solid state switching means.