3-Phase Monitor 190-480V3 Phase Voltage Phase Monitor 190 to 480VAC DIN rail or surface mount (plug in to OT08 PC socket) R rated fuses provide required short circuit protection for medium voltage motors, motor controllers and associated circuitry. These components have limited ability to absorb the energy of large short circuit currents. Medium voltage motor controllers contain overload relays which provide both overload protection and locked rotor protection to the motor.