Patent ID: 7129599

Claim:
A transfer switching apparatus comprising: (a) a first input terminal and a second input terminal each of which may be provided with AC power from one of the lines of two separate AC input buses, and an output terminal that is available for connection to one of the lines of a distribution bus; (b) a first input switch connected between the first input terminal and a junction node and a second input switch connected between the second input terminal and the junction node, the input switches responsive to control signals to open and close, the first input switch being normally closed and the second input switch being normally open, and a bi-directional transfer switch connected between the junction node and the output terminal, the transfer switch responsive to control signals to open and close the transfer switch; (c) a first rectifier connected to the first input terminal to receive AC power therefrom and provide DC output voltage to DC bus lines and a second rectifier connected to the second input terminal to receive AC power therefrom and provide DC voltage to the DC bus lines in parallel with the DC voltage provided by the first rectifier, the first and second rectifiers connected to the first and second input terminals independently of the first and second input switches; (d) a DC electrical energy storage device connected to the DC bus lines to receive DC power therefrom and deliver DC power thereto; and (e) an inverter connected to the DC bus lines and having an AC output connected to the output terminal, the inverter responsive to control signals to provide AC output voltage to the output terminal, including a controller means connected to provide control signals to the first and second input switches, to the transfer switch and to the inverter, and connected to receive signals indicating the voltage at the first and second input terminals and at the output terminal, the controller means normally controlling the first and second input switches to maintain the first input switch closed and the second input switch open and controlling the transfer switch to maintain it closed during normal availability of power at the first input terminal, and upon a fault condition of the power provided to the first input terminal controlling the transfer switch to open and controlling the inverter to provide AC output power to the output terminal, then controlling the first input switch to open, then controlling the second input switch to close, then controlling the transfer switch to close to provide AC power from the second input terminal to the output terminal while controlling the inverter to turn off and cease supplying output power to the output terminal.