Littelfuse 201A-AU-OT Three-Phase Voltage MonitorLittelfuse 201A AU OT Voltage Monitor Product Description The 201A AU is a 3 phase, auto ranging, dual range voltage monitor that protects 190 480VAC, 50 60Hz motors regardless of size. Has user adjustable 1 30 second trip delay, manual or 1 500 second restart delay, and 2 8% voltage unbalance trip point. The product also provides a user selectable nominal voltage setpoint and the voltage monitor automatically selects between the 200V and 400V range.