| 摘要 |
1288867 Protecting converters ALLMANNA SVENSKA ELEKTRISKA AB 13 Feb 1970 [14 Feb 1969] 6954/70 Heading H2F In a converting system comprising a series chain of thyristors 101 ... 104, protection against self-triggering following a-commutationperiod comprises a first polarity sensing circuit 116, 118 for determining when the anode voltage is negative, a further circuit 117, 119 for determining when the anode voltage is positive, a time delay 120, 121 interposed between one of said circuits and a AND gate 105, arranged to trigger all thyristors 101 ... 104 if the margin angle is less than the time delay t. The invention minimizes the voltage across certain thyristors that remain non-conductive if other thyristors become self-triggered. The time delay t may be adjusted in dependence on the load on the circuit by monitoring the current in a transductor 19 followed by an amplifier 20 and integrator 21. A circuit breaker 23 may operate on the A.C. side when the load is excessive. The circuit breaker 23 may also operate a by-pass switch 18 on the D.C. side of a 3-phase bridge. The conventional triggering pulses may be fed to terminal 11 either directly or via an optical link.
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