CONTROLLABLE RECTIFIER CIRCUITS WITH ENERGY RECOVERY NETWORKS

摘要

1,257,852. Commutating controlled rectifiers; inverting. WESTINGHOUSE BRAKE & SIGNAL CO. Ltd. 24 April, 1970 [29 May, 1969], No. 27379/69. Heading H2F. In a commutation circuit for a controlled rectifier (e.g. CR1) having a commutating capacitor C3 and a switching device CR7 for diverting current in an inductor L1 from the main controlled rectifier CR1, the inductor L1 is bridged by one winding of a saturable transformer T1, arranged to undergo a voltage time integral substantially the same as that of L1, another winding of the transformer being arranged to return surplus energy in L1 to the supply terminals 1, 2. As shown in Fig. 3, the invention is applied to the commutation of thyristors CR1 . . . CR6 of a three-phase bridge inverter. The transformers T1, T2 remain saturated after each commutation. One of the main thyristors (e.g. CR1) may be turned off by triggering commutating thyristor CR7 so that commutating capcitor C3 (charged by a previous commutation) can turn off CR1 by providing reverse current therethrough. L1 is initially shortcircuited by the saturated impedance of T1, but when T1 comes out of saturation, energy across L1 is transferred via diode MR7 to the D.C. supply. Reactive current is returned to the D.C. supply via diodes MR1 . . . MR6 and transformers T1, T2. In Figs. 5α . . . 5d (not shown) transformers T1, T2 are biased by bridging diodes MR7, MR8 by resistance or by means of separate biasing windings. In Fig. 6 (not shown) the right hand side of T1 is connected across L1 via a further thyristor, triggered by a circuit responsive to the voltage between point B and the left hand side of L1. In Fig. 6 (not shown) a further saturable transformer is interposed between the right hand of L1 and the cathode of MR9. Single phase inverters.-In Fig. 9, the invention is applied to an inverter comprising a bridge of four thyristors CR1 . . . CR4 having the commutation capacitor C1 across the load L. Saturable transformers T1, T2 may have a common core.