| 摘要 |
1,243,525. Electric converting systems. GENERAL ELECTRIC CO. 8 Nov., 1968 [14 Nov., 1967], No. 53055/68. Heading H2F. In a solid state converter (Fig. 2) for conversion in either sense, additional commutation reactance is provided, when operating as a rectifier, by inductors 45, 46, 47 each having a reactance X R . When operating as an inverter, switches 35, 36, 37 are closed thus shorting these inductors so that the circuit commutation reactance comprises the A.C. supply system reactance indicated by inductances 13, 14, 15 each having a reactance X s and the leakage reactance of the transformer only indicated by inductances 31, 32, 33 each having a reactance X L2 A master control unit 22 controls all the converters in the system, supplying information to respective bridge control units 23 as to firing angle for required output and mode of operation. The bridge control sends gating pulses to the valves 25-30 (each of which may be a plurality of SCR s) in dependence upon instantaneous phase voltages sensed by transformer 24. The master control 22 also actuates a relay 38 which operates a switch unit 40 via a switch trigger unit 40 to close the switches for inverting operation. The switches will not close however unless the trigger unit 39 also receives synchronizing signals from current transformers 43 or from the potential transformer 24 depending on whether voltage or current disturbances, which could cause commutation failure, predominate in a particular converter circuit. Voltage disturbances are more of a problem in inverters. The switches may be closed sequentially at zero current instants in the respective phases, and may have a jet of plasma injected between the mechanical contacts thereof at the instant of opening or closing.
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