Solid state circuit breaker with three phase capability

DETAILED DESCRIPTION This invention relates to solid state circuit breakers for controlling the supply of power from an AC supply to a load and particularly to such circuit breakers suitable for application in three-phase systems.
Copending application Ser.
No.
023,361, filed Mar.
23, 1979, by Billings and Luebrecht and assigned to the present assignee (Case W.
E.
47,975) discloses an AC solid state circuit breaker achieving the multiple objectives of good simulation of electromechanical circuit breaker characteristics, including the provision of a manual control switch for toggling between off, on and reset conditions, while doing so with apparatus whose size and weight are minimized and reliability is maximized.
The disclosure of the copending application is incorporated herein by reference including the background material referenced therein.
In the apparatus of the copending application there is provided means for providing a power removal feature for load power by locating a manual control switch so that it opens essentially all of the circuit except the static power switch branch between the source and the load.
This provides a high degree of failsafe protection for the apparatus.
A power continuity feature is provided by means for zero crossover synchronization both upon power up and power down conditions.
A circuit lock out feature is used so that on power up or turn on, operation is delayed until the occurrence of an internal power ready condition.
On power down or turn off, there is means for circuit retention subsequent to switch opening and internal power removal in order to accomplish load turn off at a desired zero crossover point of the load power through the power switch.
In addressing the requirements for a solid state circuit breaker to operate in a three phase system, or some other number of a plurality of phases, there are additional complications addressed by the present invention in order to assure effective circuit breaker operation including the power continuity feature