tripping of the poles of a multi - pole breaker requires less force from current sensing actuators , through use of a lost motion linkage including a trip link which unlatches the linkage holding one pole contact set closed before operating the inter - pole tripping elements . preferably the breaker has a fast forcing arrangement for forcing a movable contact open under short - circuit conditions , faster than the normal contact opening spring can respond . the lost motion linkage is provided by a trip link which first releases a secondary latch to permit contact opening at normal speed , and then operates an inter - pole tripping element . under short - circuit conditions the trip link engages the movable contact to force it open , between unlatching and engagement of the inter - pole tripping element .