What is thermal protection?

Thermal protection is a method of fan motor protection that is activated when a motor operating at the rated voltage locks up for some reason with the power still being supplied. It uses a thermal relay inside the motor to break the circuit to the winding coil at a temperature below the level that would cause burning.
The thermal relay is connected in series with the coil and operates by detecting the temperature of the winding coil.
Interruption temperature: Approx. 140°C
Reset temperature: Approx. 100°C
OMRON uses thermal protection on Axial Fans with diameters of 150 mm. (Ordinarily, this method is used for large Fans that cannot be sufficiently protected by impedance protection.)

Note: Be sure to turn OFF the Fan power supply before doing any inspection work.
When the motor temperature lowers, the thermal protection function automatically restarts the motor. To ensure safety, turn OFF the power supply before starting to work on the Fan.

Do not use the Fan at a temperature or voltage that exceeds the operating temperature or operating voltage.
Even with thermal protection provided, the winding will be damaged if the Fan is used when the specified operating temperature or operating voltage is exceeded.