AC/DC/EC FANS & BLOWERS
TECHNICAL SUPPORT
Insulation Class Reference
- Insulation systems are rated by standard NEMA (National Electrical Manufacturers Association) classifications according to maximum allowable operating temperatures as follows:
- T(°F) = [T(°C)](9/5) + 32
- Allowable temperature rises are based upon a reference ambient temperature of 40°C.
- Operation temperature is reference temperature + allowable temperature rise + allowance for "hot spot" winding.
- Example Temperature Tolerance Class F: 40°C + 105°C + 10°C = 155°C.
- In general a motor should not operate on temperatures above the maximums. Each 10oC rise above the ratings may reduce the motor's lifetime by one half.
- Temperature Tolerance Class B is the most common insulation class used on most 60 cycle US motors. Temperature Tolerance Class F is the most common for international and 50 cycle motors.
