Is it normal for the stepper motor to generate heat? What is the general temperature range?
1. The principle of motor heating:
The types of motors we usually see have iron cores and winding coils inside. There is resistance in the winding, and loss will occur when energized. The loss is proportional to the resistance and the square of the current. This is the copper loss we often say. If the current is not a standard DC or sine wave, harmonic loss will also occur; the core has hysteresis The eddy current effect will also produce losses in the alternating magnetic field, its size is related to the material, current, frequency, voltage, which is called iron loss. Both copper loss and iron loss will be expressed in the form of heat, which affects the efficiency of the motor. Stepper motors generally pursue positioning accuracy and torque output. The efficiency is relatively low, the current is generally large, and the harmonic content is high. The frequency of the alternating current also changes with the speed. Therefore, the stepper motor generally has a heating situation, and the situation is more general. The AC motor is serious.
2. Reasonable range of stepper motor heating:
The extent to which the motor is allowed to heat depends mainly on the internal insulation level of the motor. The internal insulation performance will be destroyed at high temperature (above 130 degrees). So as long as the inside does not exceed 130 degrees, the motor will not damage the ring, and the surface temperature will be below 90 degrees. Therefore, the surface temperature of the stepper motor is normal at 70-80 degrees. The simple temperature measurement method uses a point thermometer, and it can also be roughly judged: you can touch it with your hand for more than 1-2 seconds, not more than 60 degrees; you can only touch it with your hand, about 70-80 degrees; drop a few drops of water quickly Change, it is more than 90 degrees.
3. The heating of the stepper motor changes with speed:
When the constant current drive technology is adopted, the current of the stepper motor will be kept constant at a static and low speed to maintain a constant torque output. When the speed is high to a certain degree, the internal back EMF of the motor increases, the current will gradually decrease, and the torque will also decrease. Therefore, the heat generated by copper loss is related to the speed. The heat is generally high at static and low speed, and low at high speed. However, the change in iron loss (although the proportion is small) is not entirely the case, and the entire heating of the motor is the sum of the two, so the above is only a general situation.
4. The impact of fever:
Although motor heating generally does not affect the life of the motor, it is not necessary for most customers to ignore it. But when it is serious, it will bring some negative effects. For example, the different thermal expansion coefficients of the internal parts of the motor lead to changes in structural stress and small changes in the internal air gap, which will affect the dynamic response of the motor, and high speed will easily lose synchronization. Another example is that some occasions do not allow excessive heating of the motor, such as medical equipment and high-precision test equipment. Therefore, the necessary heating control of the motor should be carried out.
5. How to reduce the heating of the motor:
To reduce fever is to reduce copper and iron losses. There are two directions to reduce copper loss and reduce resistance and current. This requires that motors with small resistance and small rated current should be selected as much as possible when selecting models. For two-phase motors, motors connected in series can be used without parallel motors. But this often contradicts the requirements of torque and high speed. For the motor that has been selected, the automatic half-current control function and offline function of the drive should be fully utilized. The former automatically reduces the current when the motor is static, and the latter simply cuts off the current. In addition, because the current waveform is close to sinusoidal, the subdivision driver has less harmonics, and the motor will generate less heat. There are not many ways to reduce iron loss, and the voltage level is related to it. Although high-voltage driven motors will bring high-speed characteristics to improve, but also bring about increased heat. Therefore, the appropriate driving voltage level should be selected, taking into account the high speed, stability and heat, noise and other indicators.
1. The principle of motor heating:
The types of motors we usually see have iron cores and winding coils inside. There is resistance in the winding, and loss will occur when energized. The loss is proportional to the resistance and the square of the current. This is the copper loss we often say. If the current is not a standard DC or sine wave, harmonic loss will also occur; the core has hysteresis The eddy current effect will also produce losses in the alternating magnetic field, its size is related to the material, current, frequency, voltage, which is called iron loss. Both copper loss and iron loss will be expressed in the form of heat, which affects the efficiency of the motor. Stepper motors generally pursue positioning accuracy and torque output. The efficiency is relatively low, the current is generally large, and the harmonic content is high. The frequency of the alternating current also changes with the speed. Therefore, the stepper motor generally has a heating situation, and the situation is more general. The AC motor is serious.
2. Reasonable range of stepper motor heating:
The extent to which the motor is allowed to heat depends mainly on the internal insulation level of the motor. The internal insulation performance will be destroyed at high temperature (above 130 degrees). So as long as the inside does not exceed 130 degrees, the motor will not damage the ring, and the surface temperature will be below 90 degrees. Therefore, the surface temperature of the stepper motor is normal at 70-80 degrees. The simple temperature measurement method uses a point thermometer, and it can also be roughly judged: you can touch it with your hand for more than 1-2 seconds, not more than 60 degrees; you can only touch it with your hand, about 70-80 degrees; drop a few drops of water quickly Change, it is more than 90 degrees.
3. The heating of the stepper motor changes with speed:
When the constant current drive technology is adopted, the current of the stepper motor will be kept constant at a static and low speed to maintain a constant torque output. When the speed is high to a certain degree, the internal back EMF of the motor increases, the current will gradually decrease, and the torque will also decrease. Therefore, the heat generated by copper loss is related to the speed. The heat is generally high at static and low speed, and low at high speed. However, the change in iron loss (although the proportion is small) is not entirely the case, and the entire heating of the motor is the sum of the two, so the above is only a general situation.
4. The impact of fever:
Although motor heating generally does not affect the life of the motor, it is not necessary for most customers to ignore it. But when it is serious, it will bring some negative effects. For example, the different thermal expansion coefficients of the internal parts of the motor lead to changes in structural stress and small changes in the internal air gap, which will affect the dynamic response of the motor, and high speed will easily lose synchronization. Another example is that some occasions do not allow excessive heating of the motor, such as medical equipment and high-precision test equipment. Therefore, the necessary heating control of the motor should be carried out.
5. How to reduce the heating of the motor:
To reduce fever is to reduce copper and iron losses. There are two directions to reduce copper loss and reduce resistance and current. This requires that motors with small resistance and small rated current should be selected as much as possible when selecting models. For two-phase motors, motors connected in series can be used without parallel motors. But this often contradicts the requirements of torque and high speed. For the motor that has been selected, the automatic half-current control function and offline function of the drive should be fully utilized. The former automatically reduces the current when the motor is static, and the latter simply cuts off the current. In addition, because the current waveform is close to sinusoidal, the subdivision driver has less harmonics, and the motor will generate less heat. There are not many ways to reduce iron loss, and the voltage level is related to it. Although high-voltage driven motors will bring high-speed characteristics to improve, but also bring about increased heat. Therefore, the appropriate driving voltage level should be selected, taking into account the high speed, stability and heat, noise and other indicators.
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