The operating temperature of the motor is an important factor affecting its performance and life. Normally, the operating temperature of the motor should be controlled below 80°C. High temperature is one of the main causes of motor damage. When the winding temperature reaches a certain critical point, the insulation life will be shortened by half for every 8°C increase. Therefore, controlling the temperature rise of the motor is the key to ensure its stable operation and extend its life.
The concept of motor temperature rise
When running under load, the motor will generate power loss, which is eventually converted into heat energy. This will cause the internal temperature of the motor to be higher than the ambient temperature. The difference between the actual motor temperature and the ambient temperature is called “temperature rise”. When the temperature rises, the motor needs to dissipate heat to the surrounding environment. The higher the internal temperature, the faster the heat dissipation. When the motor heat dissipation speed is equal to the heat dissipation speed, the motor reaches a balanced state, the temperature no longer rises, and remains stable.
However, when the heat generation increases or the heat dissipation decreases, this balance will be broken, the temperature will continue to rise, and the temperature difference will expand. Temperature rise is an important indicator in motor design and operation, which reflects the heating condition of the motor.
Impact of temperature rise on motor performance
The temperature rise of a motor has a significant impact on its performance. If the temperature rise of a motor suddenly increases during operation, it may indicate that there is a fault in the motor, such as a blocked air duct, excessive load or burnt windings. Overheating is one of the common causes of damage to electronic and electrical equipment, especially for motors.
The temperature range of the motor is usually clearly defined by the instruction manual and nameplate. The ambient operating temperature range of general industrial motors is -20°C to 40°C, which is consistent with most industrial application scenarios. Ambient temperatures exceeding 40°C require special consideration of components such as seals, fans, insulation materials and grease in bearings of the motor.
Although the ambient operating temperature is limited to 40°C in most cases, some components of the motor, such as the windings, can run hotter by design. Some energy is inevitably lost in the form of heat. For motors with high power or low efficiency, the temperature rise allowed in the F-class insulation system may exceed 105°C.
Insulation class and temperature limits
The insulation class of a motor indicates the thermal resistance of the insulating material used. These classes are divided into A, E, B, F and H, each with specific maximum permissible temperatures and winding temperature rise limits:
| Insulation class | A | E | B | F | H |
| Heat resistant temperature | 105℃ | 115℃ | 130℃ | 155℃ | 180℃ |
The above heat resistance is not absolute, it just means that it can be used at this temperature for a long time; when the operating temperature exceeds the maximum allowable operating temperature, the service life decreases exponentially with the increase in temperature rise; therefore, the hottest point temperature of the winding insulation during normal operation of the motor should generally not exceed the limit temperature in the table.
The micro motors produced by Kinmore Motor, such as models K10, M20, N20, 030, 130, 260, etc., use insulation sheet technology with a heat resistance temperature range of 70 to 80 degrees Celsius. Models 365, 380, 540, etc. use insulation powder, which significantly improves the temperature resistance to 130 degrees Celsius. For high-voltage motors such as 7712, 7912, 9912, the temperature resistance exceeds 155 degrees Celsius.
For some products that may not meet specific temperature resistance requirements, we provide flexible solutions. If the temperature difference is not large, we can meet customer needs by adjusting the insulation material of the motor.
