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Electrical Motors - Insulation Classes

Temperature and insulation classes for electrical motors

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Electrical insulation systems are rated by standard NEMA (National Electrical Manufacturers Association) classifications according to maximum allowable operating temperature. Electrical motors will rapidly degrade if the internal temperatures exceeds the insulation temperature limits.

Insulation ClassTemperature Limit
A1) 105
B1) 130
F2) 155
H2) 180

1) Hygroscopic insulation - avoided for open and outdoor locations - shortened lifetime if condensation in the insulation occurs

2) Non-hygroscopic insulation - preferred for open and outdoor locations, higher ambient temperatures ..

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