GB1360604A - Static inverter and rectifier/inverter systems - Google Patents

Abstract

1360604 Inverting DEFENCE SECRETARY OF STATE FOR 28 June 1971 [9 July 1970] 33330/70 Addition to 1254425 Heading H2F A polyphase inverter comprises a plurality of A.C.-side and D.C.-side windings on a multilimbed core or plurality of separate cores, at least the D.C.-side windings being connected in a ring, a solid-state switching device being arranged periodically to reverse the polarity at each junction point of the ring, the A.C.-side or D.C.- side windings being graded substantially as described in Specification 1,254,425, so as to provide a substantially sinusoidal output. As shown in Fig. 3a, a large number of thyristors TH1, TH2 are turned on sequentially so as to connect a D.C. supply to tappings between primary windings of an output transformer having graded three-phase secondary windings so as to provide a substantially sinusoidal output. Thyristor TH1 is turned on at 0‹ C., the current rising linearly due to a pulse-spreading inductor T1. At 40‹ C. thyristor TH2 and transistor TK1 are turned on, giving a linear fall in current in TH1 which is thus turned off at 80‹ C. TH2 is similarly turned off by turning on TR2 at 80‹ C. The commutating voltage is regulated in dependence on the supply current. Excess energy is returned to the supply by diode D1. In Fig. 4a, each thyristor TH1, TH2 is turned off by turning off the series-connected transistor TR1, TR2. In Fig. 5 (not shown) line commutation is achieved by connecting the A.C. side to constant voltage busbars. Each thyristor is bridged by a reverse diode so that the system acts as a rectifier if the D.C. voltage becomes reduced. In Fig. 6 (not shown), antiparallel thyristors are employed for rectifying and inverting. In Fig. 7b, a diode bridge is included so as to halve the number of thyristors required in a reversible converter. In Fig. 7a (not shown) the diode bridge is replaced by a mechanical changeover switch. In Fig. 8 (not shown) antiparallel thyristors are replaced by logic triacs, the direction of conductivity of which being determined by the polarity of the trigger pulse. The thyristors may be replaced by transistors (Fig. 1, not shown), Any of the phase proportionate transformers described in Specification 1,254,425 may be employed.