Patent GB-495540-A (GB)
Title: Improvements in or relating to electric circuit interrupters of the liquid immersed type
IPC: H01H33/92
Filed: 1938-03-17
Abstract: 495,540. Liquid-blast switches. WESTINGHOUSE ELECTRIC & MANUFACTURING CO. March 17, 1938, No. 8230. Convention date, May 28, 1937. [Class 38 (v)] A method of interrupting a circuit comprises establishing an arc in an insulating liquid, maintaining the arc in a given position during at least the flow of maximum current in the current-wave, removing the gas generated by the arc from the arc stream longitudinally thereof substantially as rapidly as it is formed, thereafter, as the currentwave approaches zero moving the arc laterally in the liquid from said given position and finally subjecting the arc to a cross-blast of gas during such lateral movement. The general lay-out of an apparatus for carrying out this method is shown in Fig. 1. A cylindrical strain member 5, of insulating-material such as fibre or the material known under the Registered Trade Mark "Micarta," is secured by metal flanges 7, 9 respectively, to the annular top plate 3 of the metal casing 1 and to top plate 11, between which and a porcelain or other weatherproof casing 13 is a C-section resilient metal expansion member 21 pressing casing 13 on to subcasing 15 so that insulating liquid may fill the space between 5, 13. Arc-quenching structures 29 comprising stacks of plates, Fig. 2, are assembled on insulating rods 31 having metal ends 33 threaded to receive nuts 35, and spaced from one another by sleeves 37 and from the hanger plate 25 by sleeves 43 surrounding hanger rods 39. The movable contacts are carried by a structure comprising an operating rod 139 acted upon by an accelerating spring 147, metallic coupling members 129, and contact fingers 151 which are engageable by a contact-actuating member 153 to provide an additional gap, mechanism 159 being provided for producing a straightline motion of the structure. Each quenching unit 29, Figs. 2, 4, has a metallic top-plate 45, Fig. 5, having an aperture 47 to receive the piston 123 on the operating rod 139, an aperture 49 for the fixed contact 115, vent apertures 51 between which is an arcing-horn 117, and a vent aperture 53. Intermediate plates are perforated to form a vent shaft leading to vent 53, and a space 101 to receive the piston 123. Some have aligned elongated slots 103 having a comparatively wide part 107, in which reciprocates the movable contact 125 mounted on rod 139, and a restricted part 105, Fig. 4. U-shaped magnetic inserts 79 are provided around the slots of some of the plates. Other plates, as 61, Fig. 10, are provided with wide slots 63 formed with pockets 65 for retaining insulating liquid, these slots being separated at 68 from the aperture 67 leading to vent 53, the purpose of which is to prevent the arc from being driven beyond the end of the slot 63. A lower arcing-horn 183 is carried on the plate 95 of fibre or other insulating-material. The arc is formed initially between the contacts in the slot-part 107 and if formed at peak current, its section is larger and it is maintained in the slot-part 107 notwithstanding the bias exerted by the magnetic plates 79. The descent of piston 123 causes a rapid up-flow of oil longitudinally of the arc, which flow carries away the arc-gases produced, forcing them through the vents 51. As the instantaneous current-value decreases, and with it the arc-section, the attraction of plates 79 assisted by the piston-pressure drives the arc into the restricted part 105 on to arc-horns 117, 183, where it is subjected to a strong cross-blast of deionizing gas as a result of its engagement with the liquid in the pockets 65. In Fig. 24, the piston 191 works in a cylindrical passage 193 which communicates with the arc-passage 195 at the lower end at 199 and at the upper end at 197, 219, the arc-horn being suitably apertured at 217 so as to equalize the pressure on both sides of the piston. The fixed contact is vented at 203 for the initial products of decomposition to escape.