How to reduce stepper motor temperature

The stepper motor is a digital actuator, has been widely used in the motion control system. Many users have doubt when using the stepper motor, have a greater heat, they do not know whether this phenomenon is normal.

Heating is actually a common phenomenon in stepper motor, but what kind of heating is normal, and how to minimize the stepper motor heat?

First, we should know why the stepper motor will heat

For a variety of stepper motor, it's formed by the internal core and the windings. Winding has resistance, that will produce power loss, loss is relate with the resistance and current, this is what we often say "copper loss", if the current is not a standard DC or sine wave, it also will generate harmonic losses.

The core hysteresis eddy effects in the alternating magnetic field will produce losses, its relate with the size, materials, current, frequency, and voltage, it's called "iron loss". Copper loss and iron loss are show in the form of heat, thus affecting the efficiency of the motor.

For the stepper motor, general we pursuit the positioning accuracy and torque output, efficiency is relatively low, current is generally larger, and the harmonic components of high frequency alternating current also changes with the speed, so the stepper motor will heating, and the situation is more serious than the general AC motor.

The second, control the stepper motor heat within reasonable limits

Allow electric motor heating in what degree, that depend on the insulation. Internal insulation at high temperature (130 degrees) will be destroyed. So as long as no more than 130 degrees inside, the motor will not be damaged, and the surface temperature will below 90 degrees. Therefore, the stepper motor surface temperature at 70-80 degrees is normal.

You can use point thermometer, or use hands touch 1-2 seconds. If no more than 60 degrees, the hand can touch. If about 70-80 degrees. a few drops of water will rapidly gas disappear.

Third, the stepper motor heat changes with speed

Using constant-current drive, Under static and low speed, the current will remain relatively constant to maintain constant torque output. If speed increase certain extent, the motor back EMF increase, the current and torque will reduce. Therefore, the copper loss is related to the speed.

Generally static and low speed will bring high heat. The high speed will make low heat. However, the iron loss (although the proportion is small) changes is not always that case.

Fourth, the heat effection

Although generally the motor heat will not affect the motor life, for most users do not need to bother. However, the severe heat will bring some negative effects. The air gap change will affect the motor dynamic response, in high speed will easily out of step.

Another is the motor on some occasions does not allow excessive heat, such as medical equipment and precision test equipment. Therefore, control the heat of the motor is necessary.

Finally, reduce motor heating

Reduce heating, is to reduce the copper loss and iron loss. There are two ways to reduce the copper loss, reduce resistance and current, that require to choose low resistance and low rated current motor. It's no good ways to reduce the iron loss, it's related with the voltage levels. High voltage will bring high speed, but it also increase heat.

So we should select the right voltage level, keep balance of the high speed, stable heat and noisy etc.

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