The insulation grade of the motor refers to the heat resistance grade of the insulating material used, which is divided into A, E, B, F, and H. The allowable temperature rise refers to the limit of the temperature of the motor compared with the ambient temperature.
Temperature rise refers to the value of the stator winding temperature higher than the ambient temperature under the rated operating condition (the ambient temperature is specified to be 35 ° C or 40 ° C or less, if the specific value is not indicated on the nameplate, it is 40 ° C)
Insulation temperature class A class E class B class F class H class
Maximum allowable temperature (°C) 105 120 130 155 180
Winding temperature rise limit (K) 60 75 80 100 125
Performance reference temperature (°C) 80 95 100 120 145
In electrical equipment such as generators, insulating materials are the weakest link. Insulating materials are particularly susceptible to high temperature and accelerate aging and damage. Different insulating materials have different heat resistance, and electrical equipment with different insulating materials is resistant. The ability to heat is different. Therefore, general electrical equipment specifies the maximum temperature at which it operates.
According to the ability of different insulating materials to withstand high temperature, the maximum allowable temperature is specified. According to the temperature, they are arranged as: Y, A, E, B, F, H and C. Their allowable working temperatures are: 90, 105, 120, 130, 155, 180 and 180 ° C. Therefore, Class B insulation indicates that the insulation heat resistance temperature of the generator is 130 ° C. The user should ensure that the generator is not operated when the generator is working. The insulation material exceeds this temperature to ensure the normal operation of the generator.
Insulation grade B insulation material, mainly made of mica, asbestos, glass wool glued or impregnated with organic glue
● How high can the normal motor work at high temperatures? How high can the motor withstand?
A: If the temperature of the motor cover is more than 25 degrees above the ambient temperature, 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 wound by an enameled wire, and when the temperature of the enameled wire is higher than 150 degrees, the paint film will fall off due to excessive temperature, causing the coil to be short-circuited. When the coil temperature is above 150 degrees, the motor housing exhibits a temperature of about 100 degrees, so the maximum temperature that the motor can withstand is 100 degrees based on its case temperature.
● The temperature of the motor should be below 20 degrees Celsius, that is, the temperature of the motor cover should exceed 20 degrees Celsius, but what is the reason why the motor heats up to 20 degrees Celsius?
A: The direct cause of motor heating is caused by large current. Generally, it may be caused by short circuit or open circuit of coil, demagnetization of magnetic steel or low efficiency of motor. Normally, the motor runs for a long time and high current.
● What causes the motor to heat up? What kind of process is this?
Answer: When the motor load is running, there is power loss in the motor, which will eventually become heat energy, which will increase the temperature of the motor and exceed the ambient temperature. The value at which the motor temperature is higher than the ambient temperature is called temperature rise. Once there is temperature rise, the motor will dissipate heat to the surroundings; the higher the temperature, the faster the heat dissipation. When the heat emitted by the motor per unit time is equal to the amount of heat dissipated, the temperature of the motor no longer increases, but maintains a constant temperature, that is, a state of heat and heat balance.
●What is the general temperature increase allowed by click? Which part of the motor is most affected by the temperature rise of the motor? How is it defined?
Answer: When the motor load is running, it is better to use the load as much as possible (if mechanical strength is not considered). However, the greater the output power, the greater the power loss and the higher the temperature. We know that the weakest temperature resistance in a motor is an insulating material, such as an enameled wire. There is a limit to the temperature resistance of insulating materials. Within this limit, the physical, chemical, mechanical, electrical and other aspects of insulating materials are stable, and their working life is generally about 20 years. Beyond this limit, the life of the insulating material is drastically shortened and even burned. 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.