Automatic Phase Selector (APS) is designed to supply single phase power load from three phase four wire mains in order to maintain uninterrupted power supply of essential single-phase loads and protect them against unallowable voltage variations in the mains. For this purpose, a single-phase load is switched into a three phase circuit. Depending on voltage presence and voltage quality on phases the Automatic Phase Selector will automatically select the optimum phase and promptly switch the single phase load supply to this phase.
A phase prioritization is foreseen, therefore the APS restores the supply circuit to the user-selected priority phase after switching to reserve phases and regenerating the voltage on the priority phase. Automatic Phase Selector when used with a generator backup ensures that the ATS only starts when all the mains have been exhausted.