Abstract: A system having input terminals including line and neutral terminals for receiving AC power from a first AC source and having output terminals including output line and neutral terminals for receiving AC power from output terminals of a second AC source and for supplying AC power to a load, has a transfer switch configurable to connect the input terminals to the output terminals or to isolate the input terminals from the output terminals. When the transfer switch is configured to isolate the output terminals from the input terminals, the second AC source is caused to cease supplying power to the output terminals when after phase shifting the voltage produced by the second source the voltage at the input terminals is in-phase with that voltage.

Abstract: A system having input terminals including line and neutral terminals for receiving AC power from a first AC source and having output terminals including output line and neutral terminals for receiving AC power from output terminals of a second AC source and for supplying AC power to a load, has a transfer switch configurable to connect the input terminals to the output terminals or to isolate the input terminals from the output terminals. When the transfer switch is configured to isolate the output terminals from the input terminals, the second AC source is caused to cease supplying power to the output terminals when a first voltage signal and an input current signal indicate the voltage and the input current satisfy a first set of criteria.