CURRENT-LIMITING CIRCUIT BREAKER WITH NOWEL ARC

OF THE DISCLOSURE A current-limiting type circuit breaker including a wedge-shaped bridging movable contact which is drawn from closed position into a generally cup-shaped chamber by a high-speed solenoid. This, together with use of an ablating non-tracking insulation material (e.g. acetal resins) adjacent the closed contacts assists the transfor mation of the initial two arcs into a single arc which is elongated and moved out onto diverging arc runners into a chamber which has controlled venting, where the arc is extinguished. This case is a continuation of application Ser. No. 457,557, filed May 21, 1965, now abandoned. Our invention relates to electric circuit breakers, and more particularly to circuit breakers of the current limiting type. The great increase in the use of electric power in recent years has necessitated the provision of electric power supply systems of steadily increasing capacity, with correspondingly greater potential for causing serious damage upon the occurrence of a fault which permits short-circuit currents to flow. It is, of course, the func tion of electric circuit breakers to interrupt such short circuit currents. At such increased power supply levels, however, the provision of circuit breakers designed along conventional lines having adequate interrupt ing capacity presents increasing and at times insur mountable difficulties. In addition, and apart from the matter of interrupting capacity, it is frequently desirable to prevent fault-occasioned currents from attaining a magnitude before interruption approaching the passible maximum short-circuit current of the system. This is be cause, even though the current may eventaully be inter rupted by a circuit breaker, the passage of such high currents through other circuit components may cause damage to such components. Accordingly, it has often been necessary in prior art practice to supplement con ventional circuit breakers with auxiliary current-limiting equipment. It is a common practice, in recognition of the need just mentioned, to combine a circuit breaker with a current-limiting fuse, connected in series with it. Such circuit breaker and current-limiting fuse combinations, however, have several disadvantages. The use of fuses, which are one-time operating devices, and must be re placed after a single short-circuit interrupting operation, in a sense defeats the basic purpose of the electric circuit breaker, which is to provide a repetitively operable cir cuit protective device. In addition, the inclusion of cur rent-limiting fuses in such combinations increases the cost of the device to approximately double that of the circuit breaker itself. Furthermore, it has been found desirable to include in such combinations means whereby the blowing of the current-limiting fuse mechanically causes opening of the circuit breaker. This is achieved only by the addition of further mechanism to the com 10