Patent ID: 7259477

Claim:
An uninterruptible power supply (UPS) system comprising: an AC power input configured to receive AC power from a single-phase AC power source or a multi-phase AC power source; a DC power source; an output circuit including a power output; a controllable switch configured to selectively couple at least one of the AC power input and the DC power source to the output circuit; a processor coupled and configured to receive an input signal that indicates a single-phase AC mode or a multi-phase AC mode and provide an output signal that affects operation of the UPS depending upon which of the single-phase AC mode and the multi-phase AC mode is indicated; and a phase imbalance monitor coupled to the processor and to at least two AC input lines of the AC power input for receiving at least two corresponding voltage signals from the multi-phase AC power source, the imbalance monitor configured to provide an imbalance indication of imbalance of the at least two corresponding voltage signals, wherein the processor is configured to determine from the imbalance indication whether multi-phase operation of the UPS is applicable.