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How to deal with the motor overheating ?

During the use of the motor, the sudden temperature rise of the motor will cause the motor to be burned due to various reasons. 

So how to deal with the overheating of the motor to reduce the loss of this type of accident.

September 09, 2022

 Before solving the motor overheating, we must first understand the reasons why the motor generates heat:


1.Heat caused by motor failure. 

When the motor is running, it will fail due to various reasons. Common faults mainly include: winding short circuit or grounding, insulation damage of iron core silicon steel sheet, motor overload, winding phase loss operation, bearing damage caused by motor shaft overheating and so on. When these faults occur, it may cause the motor to overheat. Therefore, when the motor is running, pay close attention to various fault phenomena, find and deal with them in time to ensure the normal operation of the motor.


2.The copper loss and iron loss of the motor are converted into heat.

All kinds of motors we usually see have iron cores and winding coils inside. The winding has resistance, and the loss will be generated when energized. The loss is proportional to the square of the resistance and the current. This is what we often call copper loss. If the current is not a standard DC or sine wave, harmonic loss will also occur; the iron core has hysteresis. The eddy current effect also produces losses in the alternating magnetic field, and its magnitude is related to the material, current, frequency, and voltage, which is called iron loss. Both copper loss and iron loss are converted into heat, which increases the temperature of the motor, which affects the efficiency of the motor and even damages the motor. Stepper motors generally pursue positioning accuracy and torque output. The efficiency is relatively low, the current is generally relatively large, and the harmonic component is high. The frequency of the current alternating also changes with the speed. Therefore,  the stepping motor generally has heating, and the situation is more serious than the general AC motor.

 3. Influence of voltage change on motor performance.

 The influence of voltage change on motor performance. When the motor is powered by the specified AC power supply, it can better meet various performance indicators. However, the performance indicators of the actual power supply often exceed the specified deviation limit, and the deviation is quite serious in some regions and departments. When the power supply voltage is too high or too low, it will cause the motor to heat up. For example, when the power supply voltage drops, the starting torque will decrease proportionally, which will prolong the starting time, and even fail to start and burn out the motor in severe cases, which is more prominent in heavy-load starting and frequent starting applications. The rise of the power supply voltage will increase the saturation degree of the magnetic circuit of the motor, resulting in an increase in the current and an increase in the temperature rise. Therefore, the fluctuation range of the power supply voltage of the motor should be strictly controlled within the allowable range to ensure the normal operation of the motor.


4. Poor ventilation and heat dissipation cause the motor to heat up.


If the ambient temperature around the motor is too high, the ventilation duct of the motor is blocked, and there is too much sludge and dust in the motor, the heat dissipation effect will be affected. Therefore, the environment around the motor should be kept clean, the heat dissipation conditions should be improved, and the temperature rise of the motor should be reduced.


In addition, there are frequent starting and stopping of the motor or frequent forward and reverse rotation, lack of oil in the bearing, mechanical jamming and blocking, damping of the motor, and sweeping of the rotor, which will cause the motor to heat up to varying degrees.

In case of overheating of the motor, measures should be taken in time. There are two main causes of motor heating: electromagnetic problems and mechanical problems. After the motor is selected, its electromagnetic properties are determined. In the actual operation of mechanical problems, it is necessary to strengthen monitoring, pay attention to the abnormal phenomenon of motor overheating, correctly analyze the cause of motor heating, and take precautions on purpose. In practical applications, the key is how to protect the motor. Generally, a mechanical temperature control switch can be used for protection.

HCET HC01 MOTOR protector

The motor is often burnt out under the working condition of heavy load and too long running time. It can be adopted to connect the temperature control switch in series with the common lead wire end of the main and auxiliary windings. After winding, use insulating paper to bind the end of the motor winding, and then the discharge machine is close to the shell. When the single-phase motor is connected to the single-phase AC power supply, the load runs When the motor is heated due to copper and iron loss, when the temperature inside the motor is equal to the operating temperature of the temperature control switch, the temperature control switch will automatically jump off the static electric shock to cut off the power supply to protect the motor from continuing to heat up.

   There are many models of temperature-controlled switches. For selection, please refer to the "Temperature-Controlled Switch Selection Guide". The product model in the picture below is Nanjing Haichuan HCET-A type, which is a small-volume plastic case temperature control switch with a maximum contact capacity voltage of 250V-AC current of 2.5A. Operating temperature: The specification is 150℃, and the disconnecting temperature range is 150±5. The turn-on temperature range is 105±15. Parameters can also be customized upon request. If the temperature of the motor is too high for some reason during the running process, the bimetallic sheet will act due to heat and cut off the circuit to protect the motor through heat radiation or heat conduction.

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