What’s the difference of T3 and T4 in explosion-proof motors?

In explosion-proof motors, the T3 and T4 temperature markings usually indicate the explosion-proof level of the motor.  

T3 means that the motor can be used safely in hazardous environments with temperature group T3, and T4 means that the motor can be used safely in hazardous environments with temperature group T4. These markings are set based on the safety performance of electrical equipment in hazardous environments.

Specifically, the T3 and T4 markings are set based on the maximum surface temperature that explosion-proof motors that comply with international explosion-proof standards can withstand.  T3 grade means that the maximum surface temperature of the motor does not exceed 200 degrees Celsius, and T4 grade means that the maximum surface temperature of the motor does not exceed 135 degrees Celsius.

Therefore, the difference between T3 and T4 temperatures lies in the maximum temperature that the motor can withstand in different hazardous environments. When selecting an explosion-proof motor, the required explosion-proof level needs to be determined based on the specific hazardous environment and temperature conditions to ensure that the motor can operate safely and reliably.