Solid state circuit breaker with three phase capability

Claim 1

A solid-state circuit breaker for alternating current applications comprising: a static power switch for connection in multiphase paths between an AC voltage supply and loads; power supply means for developing DC voltage from the applied AC voltage supply; a manually operable control switch connected between the supply line and said supply means; zero crossover circuit means with connections both with said supply line directly and with said supply line only through said control switch and said power supply means for respectively producing a first signal indicative of the zero crossover of one phase of the AC voltage supply and also a second signal indicative that the load circuit is off; turn-on time delay circuit means for producing a signal indicative of the power supply means having achieved full operating capability after the closing of said control switch; switch detector circuit means for producing a signal in response both to the closing of said control switch and the occurrence of said time delay signal; control logic means for responding to the occurrence of said signals in a manner to produce an ON signal only when said zero crossover signal occurs and said switch detector signal occurs; drive circuit means responsive to said ON signal of said control logic means for application of signals to said power switch to initiate conduction thereof of all of said multiphase paths.