Underoil primary circuit breaker

An arc interruption assembly for an oil immersible primary circuit breaker having a fixed contact, a movable contact, and a trip-free latch mechanism for moving said movable contact into engagement with said fixed contact, said interruption assembly comprising

• a casing having a core defining first and second chambers within said casing, and
• an arc passage in said core connected to said first chamber, said fixed contact being located at one end of said arc passage and the movable contact being mounted in said arc passage for movement into engagement with the fixed contact,
• a second passage in said core connected to said second chamber,
• a first exhaust port connecting said arc passage to said second passage, a second exhaust port connecting said arc passage to said second passage and
• frangible means in said second exhaust port for opening said second exhaust port in response to high pressure gases created by a primary fault arc in said interrupter and
• means in said second chamber for venting low pressure gases from said second chamber,
• the fixed contact includes
• a conductive strip having one end bent to form a contact flange,
• a conductive ring mounted on said flange and located in the path of travel of the rod in the arc passage, and
• an electric contact supported on said strip in the path of travel of said rod whereby said rod passes through the arc ring before engaging the contact.

An underoil primary circuit breaker having a fixed contact assembly, a rod contact,

• a trip-free latch mechanism for moving the rod contact toward or away from said fixed contact assembly, and
• a trip assembly for releasing said latch mechanism in response to primary and/or secondary fault currents, the improvement comprising
• a gas blast arc interrupter mounted on said circuit breaker, said interrupter including a tubular casing, a cap on each end of said casing,
• a core positioned in said casing and defining a pressure chamber and a pressure relief chamber therein,
• an arc passage in said core connected to said pressure chamber,
• a vent passage in said core connected to said pressure relief chamber and high and low pressure exhaust ports connecting said arc passage to said vent passage whereby arc generated gases in said pressure chamber will flow across the arc passage on discharge through said exhaust ports to said vent passage, said pressure relief chamber includes means for throttling the gases flowing out of the relief chamber.

An underoil primary circuit breaker having a fixed contact assembly, a rod contact,

• a trip-free latch mechanism for moving the rod contact toward or away from said fixed contact assembly, and
• a trip assembly for releasing said latch mechanism in response to primary and/or secondary fault currents, the improvement comprising
• a gas blast arc interrupter mounted on said circuit breaker, said interrupter including
• a tubular casing, a cap on each end of said casing
• a core positioned in said casing and defining a pressure chamber and a pressure relief chamber therein,
• an arc passage in said core connected to said pressure chamber,
• a vent passage in said core connected to said pressure relief chamber and high and low pressure exhaust ports connecting said arc passage to said vent passage whereby arc generated gases in said pressure chamber will flow across the arc passage on discharge through said exhaust ports to said vent passage,
• said trip assembly includes a sensing element connected to respond to both primary and secondary faults, and a magnet positioned to respond to the temperature of the element, said magnet being released when the sensing element approaches the Curie temperature of the magnet.

An arc interruption assembly for an oil immersible primary circuit breaker having a fixed contact assembly, a movable contact, a trip-free latch mechanism for moving the rod contact into engagement with the fixed contact and a magnetic trip assembly which is responsive to the Curie temperature of a magnet, said interrupter assembly comprising

• a casing having a core defining an expansion chamber and a pressure relief chamber within said casing,
• an arc passage in said core operatively connected to said pressure relief chamber, the fixed contact being located at one end of said arc passage and the movable contact being mounted for reciprocal motion in said arc passage for movement into engagement with the fixed contact,
• a vent passage in said core connected to said relief chamber, a discharge tube in said relief chamber for discharging high pressure fluids from said pressure chamber,
• a first set of low pressure ports connecting said arc passage to said vent passage and a second set of high pressure ports connecting the arc passage to the vent passage whereby gases generated in said expansion chamber will flow across the arc passage.

An underoil primary circuit breaker having a fixed contact assembly and a rod contact,

• a trip-free latch mechanism for moving the rod contact toward or away from said fixed contact assembly, and
• a trip assembly for releasing said latch mechanism in response to a primary and/or secondary fault condition, and
• a gas blast arc interrupter mounted on said circuit breaker, said interrupter including
• a tubular casing,
• a core positioned in said casing and defining a pressure chamber and a pressure relief chamber therein,
• an arc passage in said core connected to said pressure chamber, and
• a vent passage in said core connected to said pressure relief chamber,
• high and low pressure ports in said core connecting said arc passage to said vent passage whereby high pressure gases generated in said pressure chamber will flow across the arc passage on discharge through said ports to said vent passage, said fixed contact assembly being mounted in said core at the end of said arc passage and including
• an electrically conductive contact and
• means for supporting said contact in the path of motion of said rod.