【2026 Motor Temperature】Causes of motor overheating
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What causes an electric motor to heat up? What is this process like? When the motor operates under load, there is power loss within the motor, which is ultimately converted into heat. This causes the motor’s temperature to rise above that of the surrounding environment. The value by which the motor temperature is higher than the ambient temperature is called the temperature rise. Once the temperature rises, the motor needs to dissipate heat to its surroundings ； The higher the temperature, the faster the heat dissipation. When the heat generated by the motor per unit of time is equal to the heat dissipated, the motor’s temperature stops rising and remains at a constant level, meaning it is in a state of balance between heat generation and heat dissipation.
For reference — below are the common reasons for high motor temperatures and the corresponding solutions: 1. If the motor’s actual voltage exceeds the rated voltage by more than 10%, or if it is below the rated voltage by more than 5%, this will cause the motor to heat up and its temperature to rise under rated load; in such cases, the voltage should be checked and adjusted.
2. An imbalance in the three-phase supply voltage of the motor can also cause the motor to overheat, as an imbalance in the three-phase voltage of more than 5% leads to an imbalance in the three-phase currents. The solution is to check and adjust the voltage.
3. Contact problems with the motor’s power switch or a blown fuse in one phase can both cause operation with an incomplete phase supply, which in turn leads to an increase in the motor’s temperature. The solution is to repair or replace the damaged components.
4. The wiring of the motor’s windings is incorrect, which causes the motor to overheat when operating under its rated load; the solution is to correct this wiring error.
5. A short circuit or ground fault between the turns or phases of the motor’s stator windings can cause the current in the motor to increase, leading to a rise in temperature. The solution is to apply insulation at the center or replace the windings directly.
6. Broken bars in the squirrel-cage rotor of the motor or loose connections in the windings of the wound-rotor type can cause an increase in current through the maintenance circuit, leading to overheating. The solution is to weld and repair the rotor or replace it.
7. When the bearings of the motor are severely worn, significant friction occurs, generating heat. The solution is to check whether the bearings are loose and whether there is any misalignment between the stator and the rotor.
8. An excessive load on the motor is also a cause of overheating; reducing the load or replacing it with a motor of higher power can resolve the overheating issue.
9. Excessive frequent starting of the motor, high ambient temperature, poor ventilation, and other factors can also cause the motor’s temperature to rise too high. Reducing the number of starts, lowering the ambient temperature, ensuring unobstructed air passages, removing dust and oil buildup, and maintaining proper functioning of the fan can all help address such overheating problems.
For a motor that is in operation, if the current does not exceed the motor’s rated current, it indicates that there are basically no problems with the circuit. If the original load remains unchanged, it is necessary to check whether the voltage is within the rated range; generally, 380V is considered normal within a range of plus or minus 5%. Check whether the ambient temperature is too high. Is the bearing lacking oil? Whether the cooling fan is damaged.