| 摘要 |
Method and apparatus for providing alternate current paths to a junction through different sets of gate controlled SCRs coupled to the junction. The method starts with the step of initiating a switch from an active set of SCRs to an inactive set by removing a gate signal from two parallel connected, opposite sense current carrying SCRs which in combination carry AC current in either direction. Removal of the gating signal is often initiated, for example, in response to an indication that one alternating current source is faulty so that a switch to a second source is initiated. Current is then sensed through the two SCRs of the active set to determine a current carrying state for each of those two SCRs. After the state of the current carrying SCRs is determined the current carrying state of the SCRs is confirmed during a delay time period. If the current carrying state of either of said two SCRs is the same during the delay time period, a gating signal is applied to a corresponding SCR in an inactive set to enable current flow through that corresponding SCR. Once both SCRs in the inactive set have been activated the switch is complete. By waiting until the current has been confirmed during the delay period inappropriate activation of the gate signals of an inactive switch is prevented.
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