The 201A-AU is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-480 VAC, 50/60 Hz motors regardless of size. Has user adjustable 1-30 sec trip delay, manual or 1-500 sec restart delay, and 2 to 8% voltage unbalance trip point. The product also provides a user selectable nominal voltage set point and the voltage monitor automatically selects between the 200 V and 400 V range. The Model 201A-AU includes advanced single LED diagnostics, where five different light patterns distinguish between faults and normal conditions. This unique microcontroller-based voltage and phase-sensing device constantly monitors the 3-phase voltages to detect harmful power line conditions. When a harmful condition is detected, the 201A-AU's output relay is deactivated after a specified trip delay. The output relay reactivates after power line conditions return to acceptable levels.