Insulation systems are established by standard NEMA (National Electrical Manufacturers Association) based on an average 20,000 hour motor lifetime.
This system classified maximum allowable operatingtemperatures for motors and it has been shown as below.
The maximum operation temperature is sum of reference temperature, allowable temperature rise and allowance for "hot spot" winding.
Moreover, heat is one of important factor that reduce life time of fan motor. The classification of motor insulation is indicated maximum
operating temperature. If motor is operating above maximum operating temperatures, life time of fan motor decreases rapidly Each 10°C
rise above the rating may reduce the motor lifetime by one half. It is important to be aware that insulation classes are directly related to
For example: A motor operating at 180 Degrees C will have an estimated life of only 300 hours with a Class A insulation system. If Class
B insulation is used, estimated life is increased to 1,800 hours. If Class F insulation is used, 8,500 hours of life can be expected from the
motor and with Class H insulation motor life will increase to ens of thousands of hours.