The insulation grade of the motor refers to the heat-resistant grade of the insulation materials used, which is divided into A, E, B, F and H. The allowable temperature rise refers to the limit of the motor's temperature rising compared with the ambient temperature.
Temperature rise refers to the value that the temperature of the stator winding is higher than the ambient temperature under the rated operating state of the motor (the ambient temperature is specified as 35°C or below 40°C, if the specific value is not marked on the nameplate, it is 40°C)
The temperature grade of insulation is Class A, E, B, F, H.
The maximum allowable temperature (℃) 105 120 130 155 180
The winding temperature rise limit (K) 60 75 80 100 125
The performance reference temperature (℃) 80 95 100 120 145
Insulation materials are the weakest link in electrical equipment such as generators.Insulating materials are especially susceptible to high temperature, which accelerates aging and damages.Different insulating materials have different heat resistance properties, and electrical equipment using different insulating materials has different ability to withstand high temperature. Therefore, general electrical equipment stipulates the maximum working temperature.
According to the ability of different insulating materials to withstand high temperature, people have stipulated seven allowable maximum temperatures, which are Y, A, E, B, F, H, and C in order of temperature.Their allowable operating temperatures are 90 ℃, 105 ℃, 120 ℃, 130 ℃, 155 ℃, 180 ℃ and above 180 ℃ respectively.Therefore, Class B insulation means that the insulation heat resistance temperature of the generator is 130 ℃.When the generator is working, the user should ensure that the insulation material of the generator does not exceed this temperature to ensure the normal operation of the generator.
The insulation material with insulation grade B is mainly made of mica, asbestos and glass fiber glued or impregnated by organic glue.
If the temperature of the motor cover exceeds the ambient temperature by more than 25 degrees, it indicates that the temperature rise of the motor has exceeded the normal range. Generally, the temperature rise of the motor should be below 20 degrees.Generally, the motor coil is made of enameled wire, and when the temperature of the enameled wire is higher than about 150 degrees, the paint film will fall off due to the high temperature, resulting in a short circuit of the coil. When the coil temperature is above 150 degrees, the temperature shown by the motor casing is about 100 degrees, so if it is based on the casing temperature, the maximum temperature the motor can withstand is 100 degrees.
The temperature of the motor should be below 20℃, that is, the temperature of the motor end cover should be less than 20℃ .However,the heat of the motor will still exceed 20℃ because the direct cause of the motor heat is the high current.Generally, it may be caused by short circuit or open circuit of the coil, demagnetization of the magnetic steel or low efficiency of the motor. Normally, the motor operates with large current for a long time.
When the motor is operating under load, there are power losses in the motor, which will eventually become heat energy, which will make the motor temperature rise beyond the ambient temperature.The value at which the motor temperature is higher than the ambient temperature is called temperature rise.Once there is a rise in temperature, the motor will dissipate heat around; the higher the temperature, the faster the heat dissipation.When the heat generated by the motor per unit time is equal to the dissipated heat, the temperature of the motor will not increase, but will keep a stable temperature, that is, it will be in a state of balance between heat generation and heat dissipation.
When the motor is running under load, in order to play its role as much as possible,the larger the output power, the better(if mechanical strength is not considered).But the greater the output power, the greater the loss of power, the higher the temperature.We know that the weakest thing in the motor is the insulating material, such as enameled wire.There is a limit to the temperature resistance of insulating materials. Within this limit, the physical, chemical, mechanical, electrical and other properties of insulating materials are very stable, and their working life is generally about 20 years.Exceeding this limit, the life of the insulating material is shortened sharply, and even burns out.This temperature limit is called the allowable temperature of the insulating material. The allowable temperature of the insulating material is the allowable temperature of the motor; the life of the insulating material is generally the life of the motor.
Zhejiang Ailipu Technology Co., Ltd.