Three-phase asynchronous motor
At what temperature can a motor generally work normally? What is the maximum temperature that a motor can withstand?
Answer: If the temperature of the motor cover is measured to be more than 25 degrees higher than 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 with 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, causing the coil to short-circuit. When the coil temperature is above 150 degrees, the temperature of the motor housing is about 100 degrees, so if the housing temperature is used as the basis, the maximum temperature that 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 be less than 20 degrees Celsius higher than the ambient temperature, but what is the reason why the motor heats up more than 20 degrees Celsius?
Answer: The direct cause of motor heating is due to large current. Generally, it may be caused by coil short circuit or open circuit, magnetic steel demagnetization or low motor efficiency. Normally, the motor runs at high current for a long time.
●What causes the motor to heat up? What is the process?
Answer: When the motor is running under load, there is power loss in the motor, which will eventually become heat energy, which will increase the motor temperature and exceed the ambient temperature. The value of the motor temperature higher than the ambient temperature is called temperature rise. 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 motor temperature no longer increases, but maintains a stable and unchanged temperature, that is, it is in a state of balance between heat generation and heat dissipation.
●What is the general allowable temperature rise? Which part of the motor does the temperature rise of the motor have the greatest impact on? How is it defined?
Answer: When the motor is running under load, starting from maximizing its role, the load, that is, the larger the output power, the better (if mechanical strength is not considered). However, the greater the output power and the greater the power loss, 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, and electrical properties of insulating materials are very stable, and their working life is generally about 20 years. Beyond this limit, the life of the insulating material is drastically shortened, and it may even burn 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.
