Logic-controlled solid-state switchgear for 270 volt DC

A feasibility study to design and demonstrate solid-state switch gear composed of circuit breakers and a power transfer switch is described. The switch gear operates on a nominal 270 Vdc circuit and controls power to a load up to 1 5 amperes. One circuit breaker may be interconnected to a second to form a power transfer switch. Breaker or switch on-off and transfer functions can be remotely controlled. Automatic overload trip-out is provided through an ultimate current trip and an I²t trip for transient overcrrents lower than the ultimate current trip level. A number of reclosure swith variable time delay between trip—out and reclosure are programmed and controlled by integrated analog and COSMOS logic circuits. A commutation circuit that creates minimal transient disturbances to either source or load was developed to interrupt current flow through the main SCR switching element. Laboratory tests demonstrated performance of solid-state circuit breaker (SSCB) specified voltage and temperature ranges.