• Proprietary microcontroller-based circuitry - Constant monitoring of single-phase, low-voltage, voltage unbalance, phase reversal, harmful power line conditions
• Auto-sensing wide voltage range - Automatically senses system voltage between 190-480 V ac. Saves setup time
• Advanced LED diagnostics - Quick visual indicator for cause of trip
• Adjustable trip delay - Prevents nuisance tripping due to rapidly fluctuating power line conditions
• DPDT relay output - Allows for versatility to meet wide application needs
• Manual reset - Allows for inspection of equipment before system is re-energized

The 250A is a 3-phase, auto-ranging, dual-range voltage monitor that protects 190-480VAC, 50*/60Hz motors regardless of size from low and high voltage, unbalance/single-phase and reverse-phase. The product provides a user selectable nominal voltage setpoint and the voltage monitor automatically selects between the 200V and 400V range. The 250A also features adjustable or manual restart delay. 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 Littelfuse's output relay is deactivated after a specified trip delay. The output relay reactivates after power line conditions return to acceptable levels. The Model 250A includes advanced single LED diagnostics. Five different light patterns distinguish between faults and normal conditions.