GB1252139A - - Google Patents

Abstract

1,252,139. Inductor switching arrangements for A.C. networks. LICENTIA PATENTVERWALTUNGS-G.m.b.H. 23 Dec., 1968 [22 Dec., 1967], No. 61150/68. Heading H2H The volt drop or reactive current of an A.C. network is compensated by one or more inductances each controlled by one or more pairs of anti-parallel connected semi-conductor valves, the pair(s) being in series, parallel or series/ parallel with the inductance and having at least one of the valves controlled so that switching occurs when the current of the inductance is or passes through zero. The arrangement of Fig. 1 uses one pair of valves, both controlled, connected in series with an inductance L. The inductances L, L<SP>1</SP>, L<SP>11</SP> may be star-connected, with only one valve in each pair controllable, Fig. 4 (not shown). Other arrangements disclosed are:-(1) Series-connected inductances each in parallel with a pair of valves, both controlled, Fig. 5 (not shown). (2) A series arrangement of inductance and pair of controlled valves wherein the pair and part of the inductance are shunted by another pair of controlled valves, Fig. 7 (not shown). (3) The arrangement of (2) wherein further taps are provided on the inductance for further shunting pairs of controlled valves, Fig. 9 (not shown), or wherein the remaining portion of the inductance is shunted by a further pair of controlled valves, Fig. 8 (not shown). (4) Three stepped inductances each step being connected to that of another inductance through a pair of controlled valves, Fig. 10 (not shown). To prevent the occurrence of a transient of maximum value corresponding to the disconnection at zero inductance current which occurs at a supply voltage peak, Fig. 2 (not shown), the inductance may be switched in and out as shown in Fig. 3. Switching in at point t 3 of zero supply voltage introduces an aperiodic component I d into the current waveform, such that a disconnection at zero current occurring before this component has decayed, for example at point t 4 , does not occur at a supply voltage peak and hence the magnitude of the transient is reduced. Fine and coarse compensation is described, using multi-stage inductances and capacitors of which one or a few stages are bridged by a reactive current converter providing the fine control.