Insulation classes for motor


The insulation class of the motor refers to the maximum allowable winding temperature, depend on insulating material used. There are five common rates: A, E, B, F, and H. Each rating represents a different degree of temperature resistance. If it exceeds its maximum temperature resistance during use, the motor is likely to burn out or its lifespan will be reduced.

Generally speaking, ICE motor use insulation class E(120°C), B(130°C) and F(155°C). Although the IE3 motors have lower temperature rise, we still choose F class insulation. It makes the motor more durable when operated with high temperature. For special application, such as oven or electric carrier motor, we will choose H class insulation, which help the motor withstand the higher temperature.


Insulation classes for electric equipment

In 1977, the Electric Instrument Rules Committee of the Japanese Industrial Standards Committee discussed the classes of electrical insulation and drew up JIS C 4003: Classes of electrical insulation, to clarify the classes of motor insulation and their maximum allowable temperatures.


Insulation Classification

Class Y: Withstands a temperature of up to 90°C; typically made of cotton, silk, or paper
Class A: Withstands a temperature of up to 105°C; reinforced Class-Y materials with impregnated varnish or insulation oil
Class E : Withstands a temperature of up to 120°C
Class B : Withstands a temperature of up to 130°C. This has a form that inorganic material is hardened with adhesives. This is the first insulator using this structure.
Class F : Withstands a temperature of up to 155°C; for example, made of Class-B materials that are upgraded with adhesives, silicone, and alkyd-resin varnish of higher thermal endurance
Class H : Withstands a temperature of up to 180°C; for example, made of inorganic material glued with silicone resin or adhesives of equivalent performance
Class C : insulation: Withstands a temperature of up to 180°C or higher; made of 100% inorganic material As explained above, electrical insulation is classified with its maximum allowable temperature. By adopting an insulation technique of higher thermal endurance, electric instruments can be downsized.