Influence of motor heat resistance class on insulation class

The heat resistance level marked on an electrical product usually represents the maximum temperature that the product can withstand when it reaches its intended use period under rated load and other specified conditions. Therefore, in electrical products, the temperature of the insulation used at the highest temperature should not be lower than the temperature corresponding to the heat resistance level of the product.

 

The service life of motor insulation is affected by many factors (such as temperature, electrical and mechanical stress, vibration, harmful gases, chemicals, moisture, dust and radiation, etc.) dominating factors. Therefore, there is a practical and world-recognized heat resistance classification method, that is, the heat resistance of electrical insulation is divided into several heat resistance grades. Each heat resistance grade and the corresponding temperature value are as follows:

 

The heat-resistant grade temperature (℃) is: Y90, A105, E120, B130, F155, H180; if the temperature exceeds 250°C, the heat-resistance grade is set accordingly at an interval of 25°C.

 

It is also possible to indicate the heat resistance level without letters, but the above correspondence must be followed. For equipment used under special conditions and with special requirements, the above classification method may not be applicable, and other identification and classification methods may be used.

 

The heat resistance level marked on an electrical product usually indicates the maximum temperature that the product can withstand when it reaches the expected service period under the rated load and other specified conditions. Therefore, in electrical products, the temperature of the insulation used at the highest temperature should not be lower than the temperature corresponding to the heat resistance level of the product.

 

Due to customary reasons, the term "heat resistance class" is generally used for insulating materials, insulating structures and electrical products. However, the trend in the future is that the terms "temperature index" and "relative temperature index" are recommended for insulating materials; the term "identification mark" is recommended for insulating structures; specific products; the term "heat-resistant class" is reserved for electrical products.