GB1427548A - Extinguishing arcs in electrical switching devices - Google Patents

Abstract

1427548 Extinguishing arcs SIEMENS AG 17 May 1973 [17 May 1972] 23673/73 Heading H1N Arc runner electrodes 2, 3 in an electrical switch have first portions defining a " circulatory " (i.e. closed, e.g. annular) path that an arc will follow, under the influence of a magnetic field generated as a function of the arc current, if the arc current is sufficiently high; the electrodes also having second portions 20, Fig. 4, defining between them an additional path for the arc, the additional path leading off from the circulatory path at a transition location at which when the arc current is sufficiently low the arc will migrate from the circulatory path to move along the additional path thereby to become quenched by contact with a cooling surface provided by a solid electrically insulating body 21 of the switch. An arc formed between switching contacts 5, 6 migrates to gap a between arc runner electrodes 2, 3 assisted by blow out coils 14, 15. Electrodes 2, 3 may be identical or one may be replaced by a metal sheet (134, Fig. 15, not shown). The second portions of the electrodes may, as Fig. 1, be spaced axially or be side-byside (Figs. 5, 6, not shown). There may be a plurality of additional paths (Figs. 10-13, not shown). The arc may be caused to follow the additional path when the arc current is low and thus also the Lorenz force tending to keep the arc on the circulatory path is low, by means of either an air gap (as shown in Fig. 4), permanent magnets (Figs. 7-13, not shown) or pneumatically (not shown). So that the arc, if not extinguished on the additional path (e.g. if the instantaneous arc current increases) may return to the circulatory path, the second portions of the electrodes may reapproach the first portions at an end (as in Fig. 4) or at an intermediate point (Fig. 14, not shown) or rejoin (Figs. 7-13, not shown) the first portions. The arc runner electrodes may be in a sulphur hexafluoride quenching atmosphere. The cooling members 21 may be ceramic, e.g. aluminium oxide or mica or asbestos with a rough or porous surface. The electrode portions defining the additional path may be divergent in the direction of travel of the arc. The blow out coils may have induction rings inducing a phase shift between arc current and the magnetic field produced thereby (30, 31, Fig. 5, not shown).