GB939459A - Improvements in and relating to arc gap devices - Google Patents

Abstract

939,459. Surge diverters. LICENTIA PATENT - VERWALTUNGS - G.m.b.H. Aug. 14, 1962, No. 31129/62. Class 38 (4). A magnetic blow-out arc gap device having preionising means comprises electrodes 14, 15 which are shaped and spaced to form an ignition gap 16 and a preionising gap 17 containing an insulating insert 18 maintained in contact with electrodes 14, 15 by springs 28, 29 acting thereon. The response voltage of the device is determined by the thickness of the member 18 which projects laterally beyond electrodes 14, 15, Fig. 3 (not shown). The electrode leads 19, 20 are crossed-over to obtain a magnetic blow-out effect and are separated by an insulating member 21. The device has a two-part insulating housing 22, 23 (Fig. 5) which forms an arc chamber 30 and vent 33, the inner walls of parts 22, 23 having interengaging zig-zag corrugations 39, 40 for increased arc quenching. Magnetic induction in the arc zone may be increased by providing a second housing of two soft iron parts 41, 42 insulated from the parts 22, 23 by shells 44, and slotted to prevent the passage of induced currents, Fig. 6 (not shown). The preionising gap may be formed in a plane at right angles to that shown in Fig. 2 by shaping the electrodes as shown in Fig. 9 and superimposing them with the insulating member positioned at the point 53 to provide the preionising gap, Figs. 7 and 8 (not shown). Fig. 11 shows another modification of the electrode arrangement of Fig. 2 in which the limbs 58, 59 of a V-shaped electrode are disposed one on each side of an insulating plate 57 which is positioned between the electrodes 60, 61 in such a way that the length of the arc path is approximately doubled. In Fig. 12 the insulating housing of the device carries segments 78, 79 of voltage control resistance material provided at their upper and lower sides (together with adjacent parts of the housing) with metallic cladding 80 which is connected to an electrode lead 88. The other lead 89 is connected to cladding 90 formed as a semi-circular annulus, the loops of metallic cladding increasing the magnetic blast effect on the arc. A number of arc gap devices as shown in Fig. 12 may be arranged in the bores of current limiting resistances to form an excess voltage diverter as for example in the manner shown in Fig. 14, where the device 93 is connected in series (under fault conditions) with resistances 91, 92 through supports 94, 95 whose contacts 97, 98 engage the metal cladding of the device, insulating members 96, 99, 100, 101 being provided. Rotation of contacts 97, 98 is prevented by slots (not shown) in the device housing.