Abstract: An electric circuit breaker comprises first and second contacts, which engage each other while the circuit breaker is fully closed and both of which are movable. During the initial portion of an opening operation, the two contacts move together and remain engaged. First electromagnetic-assist means develops while the contacts are engaged a magnetic force on the first contact varying directly with current through the contacts which urges the first contact toward the second contact. Second electromagnetic-assist means develops while the contacts are engaged a magnetic force on the second contact varying directly with current through the contacts which urges the second contact toward the first contact. Means is provided to block motion of the first contact with the second contact after initial opening motion of the second contact and to prevent during subsequent opening motion of the second contact the transmission of force from the first electromagnetic-assist means to the second contact.

Abstract: Discloses a method of detecting a leak in any one of the vacuum-type circuit interrupters of a high voltage vacuum circuit breaker comprising a plurality of normally series-connected interrupters located within a tank of the circuit breaker containing pressurized gas. Through small openings in the wall of the tank, a first set of conductive rods are inserted to make electrical connection with predetermined terminals of the interrupters. Through other small openings in the tank wall, a second set of conductive rods, insulated from the tank wall, are inserted to make electrical connection with predetermined other terminals of the inrterrupters. These predetermined terminals are such that the interrupters are connected electrically in parallel between the first and second sets of rods.