Abstract: A circuit breaker having a pair of main contacts for carrying electrical current flow during closed contact operation is provided with a pair of concentric auxiliary electrodes and magnetic means for rotating an arc produced by the arc current at the opening of the electrodes and puffer means for supplying a compressed flow of arc extinguishing gas between the auxiliary electrodes when the circuit breaker is opened. In one example, each auxiliary electrode has a magnetic means located therewithin to produce a self-induced magnetic field which drives the arc around the circumference of the auxiliary electrode. In an alternative embodiment, one auxiliary electrode included a rapidly expanding nozzle, and the other auxiliary electrode is shaped as a solid cylindrical pin located concentric with said nozzle. In the preferred embodiment, the insulating gas comprises sulfur hexafluoride.

Abstract: A puffer breaker employs a low energy actuating mechanism during normal opening and closing operation and a pyrolytic cartridge actuating mechanism for high speed operation under fault conditions. A current detector is provided in circuit with the puffer breaker to control operation of the actuating mechanisms, so that whenever a fault condition is detected, the pyrolytic cartridge actuating mechanism rapidly opens the circuit breaker.

Abstract: A puffer-type circuit breaker is provided with a nozzle of insulating material having a section downstream of the nozzle throat designed to optimize arc cooling by a high speed flow of insulating gas passing over the arc. The nozzle design prevents excessive ablation of nozzle material by the arc and reduces blocking of the nozzle by the moving electrode during circuit interruption. The nozzle includes a generally conically-shaped upstream section, a throat section and a generally bell-shaped downstream section.

Abstract: Current interruption capability for short-line or terminal faults is achieved by connecting a fluid blast interrupter in series with a high current vacuum interrupter capable of withstanding the initial recovery voltage during such fault. The fluid blast breaker ultimately becomes able to carry the total recovery voltage by delaying opening of the vacuum interrupter for a fixed interval after opening of the fluid blast breaker has been triggered.

Abstract: A puffer-type circuit interrupter comprises a cylinder coupled to the conductive contact rod of the interrupter and a floating piston within the cylinder that is relatively movable with respect to the cylinder to pressurize fluid in the cylinder, which pressurized fluid is used for arc-extinguishing purposes. Means effective during an interrupting operation is provided for forcing current flowing through the rod to follow a loop-shaped path, electrically in series with the rod, that extends through the piston. This current has a magnetic effect while flowing through said loop-shaped path that acts to drive the piston within the cylinder through a fluid-pressurizing operation.