Littelfuse 250A-MET Three-Phase Voltage Monitor (Replaces META)Littelfuse 250A MET Voltage Monitor Product Description (Replaces META) Model 250A MET is an auto ranging voltage monitor designed to protect 3 phase motors regardless of size. It is used on 190 480VAC, 50 60Hz motors to protect the motors from damage caused by low voltage, voltage unbalance, single phasing and reverse phasing. A unique microcontroller based voltage and phase sensing circuit constantly monitors the three phase voltages to detect