Patent ID: 8212402

Claim:
An uninterruptible power supply (UPS) system comprising: an input to receive input power having an input voltage; an output to provide output power; a neutral line; an automatic voltage regulation (AVR) transformer coupled to the input and the output of the UPS and having an input, an output, a core and a plurality of switches controllably coupled to at least one of the core, the input and the output; a bypass switch configured to selectively couple the core of the AVR transformer to the neutral line; and a controller configured to control the plurality of switches of the AVR transformer and the bypass switch, wherein the controller is configured to control the bypass switch to isolate the core of the AVR transformer from the neutral line in a first mode of operation and to couple the core of the AVR transformer to the neutral line in a second mode of operation, and wherein the controller is configured to, in the first mode of operation, couple a first one of the plurality of switches of the AVR transformer to the core and the AVR transformer input and a second one of the plurality of switches of the AVR transformer to the core and to the AVR transformer output in a configuration of the UPS to provide an output voltage of the AVR transformer that is equal to an input voltage at the input of the UPS.