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Insulation Level of Explosion-Proof Motor

When discussing insulation levels, the issue of temperature rise in explosion-proof motors becomes relevant. In fact, there are two key points on which consensus needs to be reached:

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Class F Insulation:

Currently, over 90% of high and low voltage explosion-proof motors in China are Class F insulated. To extend the lifespan of explosion-proof motors, more than 90% of manufacturers indicate “Class F insulation, temperature rise assessed by Class B limits” in their samples. Class B insulation allows a temperature of 130°C, while Class F permits up to 155°C. Considering an environmental temperature of 40°C, manufacturing process and material fluctuations of 5°C and 10°C, the factory temperature rise limit for Class B insulated explosion-proof motors is set to 80K, and for Class F, it is 90K (95K for underground explosion-proof motors).

Class H Insulation:

Class H insulation permits a temperature of 180°C. However, the design, manufacturing, bearings, and lubricants for Class H explosion-proof motors are not yet widely applied in China. For manufacturers, producing Class H insulated windings is not difficult; the challenge lies in high-temperature bearings. Therefore, unless necessary (such as in environments with temperatures of 60°C, or where explosion-proof motor size is limited), the use of Class H insulated explosion-proof motors should be avoided.



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