Circuit interrupter having an insulated bridging contact

Abstract

A circuit interrupter particularly suitable for use in an oil filled distribution transformer having an elongated contact arm pivotable about one end with a movable contact attached to the other end through suitable insulating members to electrically isolate the movable contact from the elongated contact arm. The movable contact is a bridging contact for completing a series circuit through two stationary contacts. The movable bridging contact is spring biased away from the elongated contact arm. A retainer restricts the movement of the bridging contact away from the insulating members attached to the elongated contact arm. The biasing spring is disposed between the insulating members and the retainer. Grooves formed in the sides of the insulating members restrict rotational movement of the retainer and bridging contact. For larger circuit interrupters, a bridging contact assembly can be utilized having a plurality of parallel bridging contacts and a plurality of biasing springs. The elongated contact arm is biased towards an open position when the bridging contact is separate from the stationary contacts, but with the circuit interrupter in the normally closed position is held in a closed position wherein the bridging contact is in engagement with the stationary contact. A latching mechanism which is responsive to a bimetal or magnetic trip to allow the circuit breaker to trip open during overload conditions, holds the elongated contact arm in the closed position.