GB1425641A - Vacuum switches - Google Patents

Abstract

1425641 Vacuum switches SIEMENS AG 12 June 1973 [19 July 1972] 27869/73 Heading H1N A vacuum switch has separable disc-shaped contacts 4, 5 each with a central recess 9 and with respective solid rod conductive support members 7, 6 arranged in a known manner (Fig. 1) but the movable contact 5 has its thickness reduced by means of an annular recess 11 thus forming a peripheral zone which is also electrically connected to the support member 6 by means of four current-carrying loops 12 of quadrantal shape and spaced coaxially around the support member in a plane parallel to and rearward of the contacting surface (Figs 2, 3). The conductivity of the support member 6 is high in relation to that of the loops which, by being arranged in parallel, have a low inductance so that under circuit breaking conditions an arc which is first struck eccentrically by reason of the central recess 9 then moves radially and tangentially outwards under the influence of magnetic fields created by the current flow in the high conductance path of the movable contact before finally coming under the strengthening blow-out field created by eddy currents in region of the annular recess 11 in conjunction with the change in current distribution as between the central zone and the peripheral zone which occurs when the arc crosses the recess. In modifications the annular recess 11 can contain a ring of magnetically permeable material or the reduction in thickness can be a discontinuity thus giving the peripheral zone of contact 5 a separate entity with the loops 12 in parallel acting both as current carriers and physical supports.