ES356615A1 - Circuit interrupter having dual-bore arc extinguishing means - Google Patents

Abstract

A circuit interrupter 100 comprises a tubular insulating casing 32, annular blocks of arc extinguishing material 122, 124, 126, 128, e.g. of boric acid housed in casing 108, each having aligned large and small bores 130, 192 with a conducting rod 83, 182 disposed in each, each block having in its face contracting other blocks a recess (126b in Fig. 3, not shown), extending around and spaced from the small bore 192, each recess having an opening to the periphery of the block, a bonding material, e.g. epoxy resin, filling adjacent pairs of said recesses. The fuse unit 100 is supported by insulators 272 and 282 with contact 250 latching the upper terminal 34 and contact 260 pivotably supporting lower terminal 36. Conductive elements 160, 162 and 194 connect the rods 83 and 182 to terminal means 150. The fusible element 160 is of lowest resistance of the three elements and under overload conditions fuses first, followed by strain member 162. When strain member 162 fuses the conductive rods 83 and 182 joined by pin 184 at their top ends are moved upwards under the influence of spring means 76, stretching the helically coiled wire 194 until it either fuses as it is carrying the full current or else is mechanically broken. Arcing will take place at this breakage and will usually occur between the end of the rod 182 and the arcing terminal 158, which is coated with a thin layer of insulating enamel. When interrupting low currents, e.g. less than 1000 amps the arc will be extinguished by gases produced in the arc extinguishing material of the small bore 192, but with larger currents the arc may then restrike in the main bore 130 from the retreating end of rod 83, where it is normally extinguished. The epoxy filled recesses around the small bore prevents ionized gases from travelling between bores. With still higher currents the temperature and pressure in the box may rise to a dangerous level in which case the thin walls 126A and 128A between C-shaped recess 129 and the bore 130 will rupture to reduce the pressure. The conductive rod 83 is connected to the upper terminal 36 by flexible cables 82 and conductive member 60. When the spring collapses after fusion of the strain member, the member 74 to which the upper end of the spring is secured slides over the member 60 under the reaction of the spring and pin 56 which is secured to the spring moves in slot 62 of member 60 and tripping member 52 integral with the pin 56 moves through the hole 46 in cap 44. The tripping member 52 detaches the latching means 250 and fuse unit 100 drops out of contact with the upper contact pivoting on the lower terminal means 260. Pivotable means 274 is provided on the upper terminal 34 to allow opening and closing of the connection through the fuse unit using a hook stick.