The MotorSaver 50R Series Single-Phase Voltage Monitor voltage sensing circuit constantly monitors the single-phase power for a low voltage condition. When a harmful condition is detected, the 50R Series output relay is deactivated after a fixed trip delay time. The output relay reactivates after power line conditions return to an acceptable level for a fixed restart time delay period. The trip delay prevents nuisance tripping due to rapidly fluctuating power line conditions. Single-phase motors on fans, compressors, air conditioners, heat pumps, water pumps, and small conveyor motors can be protected by the 50R Series.