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 grades. The allowable temperature rise refers to the limit of the temperature rise of the motor compared with the ambient temperature.
Temperature rise refers to the value of the temperature of the stator winding 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).
In electrical equipment such as generators, insulating materials are the weakest link. Insulating materials are especially susceptible to accelerated aging and damage due to high temperature. Different insulating materials have different heat resistance properties, and electrical equipment using different insulating materials have different resistance The ability of high temperature is different. Therefore, general electrical equipment stipulates the maximum temperature of its work.
According to the ability of different insulating materials to withstand high temperatures, seven allowable maximum temperatures have been stipulated, which are arranged according to the temperature: Y, A, E, B, F, H and C. Their allowable operating temperatures are: 90, 105, 120, 130, 155, 180 and above 180°C. Therefore, Class B insulation means that the heat-resistant temperature of the insulation used in the generator is 130°C. 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.
Insulation materials with insulation class B are mainly made of mica, asbestos, and glass filaments glued or impregnated with organic glue.
Generally, at what temperature can the motor work normally? What is the maximum temperature the motor can withstand?
Answer: If the measured 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 motor casing exhibits a temperature of about 100 degrees, so if the casing temperature is used as the basis, the maximum temperature the motor can withstand is 100 degrees.
The temperature of the motor should be below 20 degrees Celsius, that is, the temperature of the motor end cover should exceed the ambient temperature by less than 20 degrees Celsius, but what is the reason for the motor to heat up more than 20 degrees Celsius?
Answer: The direct cause of the motor heating is due to the large 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. The normal situation is that the motor runs at a high current for a long time.
What causes the motor to heat up? What kind of process is this?
Answer: When the motor is running under load, there is power loss in the motor, which will eventually turn into heat energy, which will increase the temperature of the motor and exceed the ambient temperature. The value by which the motor temperature rises above the ambient temperature is called warm-up. Once the temperature rises, 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 heat dissipated, the temperature of the motor will not increase, but maintain a stable temperature, that is, in a state of balance between heat generation and heat dissipation.
What is the general click allowable temperature rise? Which part of the motor is most affected by the temperature rise of the motor? How is it defined?
Answer: When the motor is running under load, from the perspective of exerting its function as much as possible, the higher the load, that is, the output power, the better (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-resistant 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 aspects of insulating materials are very stable, and their working life is generally about 20 years. If this limit is exceeded, the life of the insulating material will be shortened sharply, and it may even be 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.