Patent GB-479728-A (GB)
Title: Improvements in or relating to electric circuit breakers having arc extinguishing devices
IPC: H01H33/18
Filed: 1937-06-04
Abstract: 479,728. Liquid blast switches. WESTINGHOUSE ELECTRIC & MANUFACTURING CO. June 4, 1937, No. 15582. Convention date, June 5, 1936. [Class 38 (v)] An arc-extinguishing structure comprises means of insulating-material for defining the walls of a slot-like, substantially-enclosed, arc passage, means for drawing an arc longitudinally of the passage, and means for moving the arc laterally along the passage, the walls of the passage being generally convergent in the direction of arc-movement from the zone of arc-initiation for gradually restricting . the cross-section of the arc, and having opposed, inwardly-projecting, longitudinally-spaced ribs for further restricting portions of the arc, additional means being positioned rearwardly within the passage for impeding the movement of the arc along the passage. Fig. 1 shows part of a structure comprising a number of extinguishing units 13, each associated with one of a number of series-connected breaks, the structure being secured by a casting 75 to the lead-in conductor 11 in a, liquid-tank. Fig. 2 is a developed sectional view taken longitudinally through the arc-passage of a unit 13. Each unit comprises a stack of circular insulating plates 16 ... 20 for defining the passage 51 and insulating end plates 15 for closing the passage-ends, the whole being secured between magnetic end plates 60, 61 by through bolts 49. Each plate 16 has a slot 21 with an enlarged end 22, Fig. 3, whereas each plate 17 has a corresponding slot of narrower width than 21 and an enlarged end which is smaller than the end 22. Each plate 18, Fig. 5, has a slot 25 with an enlarged end 26 similar to that 22, and indentures 27 so formed as to leave gaps 28 ... 31 of progressively-decreasing width. The plates 20 are similar to those 18, but the indentures therein are staggered with respect to those of the latter, so that the centres of their indentures lie over the gaps 28 &c. of plates 18. In both. sets of plates 18, 20, the portions 32, 42 between the remote indentures 27 are left in full. The plates 19, Fig. 6, are slotted at 33 and have an enlarged end 35 similar to that of plates 17. - The slots 33 taper to an intermediate part of uniform width and then taper again, these slots defining the general shape of the arcpassage horizontally. Slots 21 in plates 16 are of uniform and relatively-great width to accommodate arc-horns 53, 55, with tips 91, 101, whereas the indentures 27 form liquid-retaining pockets. As the arc moves along the horns 53, 55 away from the tips, which are located - adjacent the widened end of the passage 51 formed by the slot-ends, the tapering form of the passage gradually contracts it, so lessening the current-density therein and hence its tendency to move back into the enlarged part of the passage. The successive ribs 57 between the indentures 27 further restrict the arc and the liquid retained in the indentures is decomposed into unionized gas which penetrates the arc. The parts 32, 42 between the remote indentures impede the movement of the arc which, in the case of heavy currents, might otherwise be driven to the remote end of the passage 51 before it is quenched. To provide for escape of arc-products, conduits 107 in plates 60, 61 lead into annular spaces 105 in plates 16, the spaces 105 being in communication with the slots 21 over ports 106 and recesses 109 in the arc-horns. The movable contact 69 is guided by member 70 in the lower end-plates 15, 61 and is actuated by linkage 71 pinned at 72 to an axially-arranged, operating- rod 73 common to all the units 13. Magnetic blow-outs.-For moving the arc along the passage 51, a radial magnetic field is set up by coils 65, 67 embedded in magnetic plate 60, and coil 67 in magnetic plate 61. Fixed contact 68 is secured to one end of coil 65, the other end of which is connected over screw 81 and parts 79, 77 to casting 75. Connection from movable contact 69 is over shunt 83, bracket 85 and conductor 87 to the unit 13 below. The upper coil 67 is connected at one end 93 to connector 79 and at 94 to the horn 53 so as to be energized when the upper end of the arc is transferred to the horn 53 by coil 65. Lower coil 67 is connected at one end 96 to horn 55, which is connected at 97 to end plate 61, and at the other end 98 to one end of the upper coil 67 of the unit 13 below. When the arc in the unit 13 below is moved to its arc-horn 53, the upper coil 67 of that unit and the lower coil 67 of the upper unit are connected in series and the arc in the upper unit is thus transferred to its horn 55. Specification 454,186 is referred to.