Motor Protection

Reverse polarity protection function (DC fan)

To prevent failure, the fan is designed to cut off current when power leads are connected in reverse. It will operate normally once the leads are connected correctly.
However, note that reversing the positive and negative power leads may cause failure if the sensor wire of a sensor fan or the control wire of a PWM control fan is connected.

Burnout protection function at locked rotor condition (DC fan, ACDC fan)

Current cutoff system
If the fan blades are restricted, the coil current is cut off at regular cycles to prevent overheating of the coil. When the hindrance is removed, the fan restarts automatically.

Burnout protection function at locked rotor condition (AC fan)

Impedance protection (60 mm sq., 80 mm sq., 92 mm sq., 120 mm sq.)
This system is used for shading coil-type fans. When the blades are restricted, the current is reduced by the impedance of the coil itself to prevent a temperature rise in the coil. However, if the applied voltage exceeds the specification range, an overcurrent can occur and result in overheating, and so care needs to be taken.

Thermal protection (160 mm sq., ø172 mm)
This system is used for condenser phase-type fans. A temperature sensor is incorporated in the coil so that if the temperature exceeds the specification temperature, the current is cut off to prevent overheating of the coil.

Last updated: November 2025