UPS med mekanisk skifterelæ-lysbuesvækkelse

Systems and methods of providing power with an uninterruptible power supply are provided. The uninterruptible power supply includes a first input to receive an input AC voltage from a power source, the input AC voltage having an associated phase angle, and a second input to receive an input voltage from a backup power source. The uninterruptible power supply also includes an output. The output provides output power derived from power from at least one of the power source and the backup power source. The uninterruptible power supply also includes an inverter coupled to the backup power source, a relay and a controller. The relay is configured to couple the first input with the output in a first position, and to couple the inverter with the output in a second position. The controller is configured to detect a voltage swell condition of the input voltage, and responsive to detection of the voltage swell condition, control the relay to switch from the first position to the second position during a predefined range of phase angles of the input AC voltage.