What are the causes and solutions for the heating of the stepper motor?

Update:05 Sep 2019

Heating is a common phenomenon in stepper motors, but w […]

Heating is a common phenomenon in stepper motors, but what kind of heating is normal, and how to minimize the heating of stepper motors? The following is a simple analysis.
1, the reason for stepper motor heating
1. Why does the stepper motor heat up? For various stepper motors, the inside is composed of a core and a winding coil. The winding has resistance, and the power will generate loss. The loss is proportional to the square of the resistance and current. This current is not a standard DC or sine wave, and it Washing Machine AC Motor Factoryalso produces harmonic loss. The core has a hysteresis eddy current effect, and in the alternating magnetic field. Loss will occur, the size of which is related to material, current, frequency, voltage, which is called iron loss. Both copper loss and iron loss are manifested in the form of heat, which affects the efficiency of the motor. The stepping motor is relatively large, and the harmonic components are high, and the frequency of the alternating current also varies with the rotational speed. Therefore, the heating of the stepping motor is generally more serious than that of the general AC motor.
2. A reasonable range of stepper motor heating to what extent the motor heat is allowed, mainly depends on the internal insulation level of the motor. Internal insulation performance at high temperature (130 degrees as long as the internal does not exceed 130 degrees, the motor will not be damaged, and the surface temperature will be below 90 degrees, the stepper motor surface temperature is normal at 70-80 degrees. Simple temperature measurement The method is useful for point temperature meter, and can also be roughly judged: the hand can be touched for more than 1-2 seconds, not more than 60 degrees, and can only be touched by hand, about 70-80 degrees, and a few drops of water quickly vaporize, then 90 More than the degree.
3. The stepper motor heat is constant with the speed change to maintain the constant torque output. When the speed is high, the internal back EMF of the motor rises, the current will gradually decrease, and the torque will drop. It is related to the fever caused by copper damage. Static and low speed are not always, and the whole heat of the motor is the sum of the two. The above is just the general situation.
2, the solution to the heating problem of the stepper motor
1. Reduce the heat generated by the motor to reduce heat, that is, reduce copper loss and iron loss, reduce copper loss in two directions, reduce resistance and current, which requires selecting a motor with small resistance and small rated current when selecting the model. Two-phase motors, which can use series motors, do not use parallel motors, but this often contradicts the requirements of torque and high speed.
2. For the motor that has been selected, the automatic semi-flow control function and the offline function of the drive should be sufficient. The former automatically reduces the current when the motor is static, and the latter simply cuts off the current.
3. In addition, the subdivided driver current waveform is close to sinusoidal, with less harmonics and less motor heating. There are not many ways to reduce iron loss, and the voltage level is related to it. Although the high-voltage drive motor will bring about the improvement of high-speed characteristics, it also brings about an increase in heat.
4. The appropriate driving voltage level should be selected, taking into account high band, smoothness, heat and noise.