Novatek pef 301 phase inverter automatic phase selector switch novatek pef 301 p the novatek pef 301 universal automatic electronic phase switch is designed to supply a single phase 220v 50hz appliance from a three phase four wire mains supply 3x 380 n in order to maintain an uninterrupted power supply for essential single phase equipment and protect it against unallowable voltage variations in the mains p p to this end a single phase load is connected to the three phase mains via th