Class of insulation

The main component for electric motor is a stator.What is stator?Basically stators are wound with insulated windings made from cooper wire.The insulation  materials for winding of stator such as polyester, poly vinyl formal,polyurethane etc.

The main purpose of insulation is to protect the windings in the slots of the stator lamination and layer between winding coils.The insulation class is durability factor depend on whole of insulation condition.

According from IEEE regulation,The classification of insulation electric motor have a deference rating for maximum temperature that insulation winding can operate.We can see the insulation class at  motor nameplate.Please refer the table below for insulation class rating temperature.

Classification of insulation for electric motor.


Electric motor manufacture design the  winding insulation class depend on technical aspect and user application.For good grade of insulation,the cost is higher.So the engineer selects the electric motor based on applications and working area temperature characteristics.

The temperature for electric motor is depend on the fans performance and design.Manufacture normally design the cooling fan according to the duty,type of application and load on the motor.Theoretically the load on motor affected the temperature of motor.

The conclusion is,when we selected the class of insulation for electric motor,several factor must be consider are :

  • Type of load ( pump,turbine,compressor)
  • Working area ambient temperature
  • Application of motor
  • Room condition


Lemau is Owner of .Involved in Electrical & Automation Engineering since 2001. Passionate to shared all experience & knowledge about Electrical.

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  1. When you say type of load you should consider duty too-continuous,intermittent,periodic,fluctuating,% overload etc

  2. DALJEET SINGH says:

    class temp
    you(y) 90
    are(a) 105
    extra(e) 120
    beautiful(b) 130
    from(f) 155
    her(h) 180
    cousin(c) above 180

  3. Anil Kumar says:

    Can anyone tell me about the calculation of the winding wire size and the driven temperature.

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