Abstract: An arc suppression circuit in a protection relay having trip contacts is used to turn off a battery-powered solenoid and trip an AC power circuit breaker. The arc suppression circuit uses a switch-control circuit to control the turning off of a semi-conductor switch so that the semi-conductor switch provides a current path around the trip contacts, and is carrying all, or substantially all, of the load current, before the trip contacts are opened. When the trip contacts begin to open, the switch-control circuit holds the semi-conductor switch on for a sufficient time to prevent an arc from becoming established before turning the semi-conductor switch off. In a second embodiment, the arc suppression circuit provides a second switch-control circuit. This second switch-control circuit is configured to accept control signals from a microprocessor within a protection relay.

Abstract: An oil-immersed circuit breaker is provided having a mechanical/magnetic trip indicator. In a preferred embodiment, the trip indicator comprises a mechanical drive train (coupled to a conventional trip-sensing mechanism), a push piece, and an indicator piece. The drive train and the push piece are located inside the enclosure immersed in oil. The indicator piece is located outside the enclosure. The push piece is magnetically coupled to the indicator piece. Magnetic coupling eliminates problems encountered with prior art trip indicators associated with oil-seal leakage, electrical component failure, and power source failure.