1. Cause of Motor Heating
It is normal for any motor to heat up during operation, and stepper motors are no exception.
A stepper motor consists of an iron core and winding coils. The winding coils have inherent electrical resistance, and current flowing through the motor causes power loss. This loss is proportional to the resistance and the square of the current (I²R loss), commonly known as copper loss. In addition, the iron core experiences hysteresis loss and eddy current loss in the alternating magnetic field. These losses depend on the core material, current, frequency, and voltage, and are collectively referred to as iron loss. Both copper loss and iron loss are dissipated as heat, which reduces motor efficiency.
Stepper motors are designed for high positioning accuracy and torque output, which inherently results in lower efficiency and higher operating currents. Additionally, the current waveform contains significant harmonic components, and the current frequency varies with speed. As a result, stepper motors generally run hotter than other motor types.
2. Maximum Allowable Temperature
The allowable temperature rise of a motor depends primarily on its internal insulation class. The internal insulation will be compromised only at excessively high temperatures (above 130°C). Therefore, as long as the internal temperature remains below 130°C and the surface temperature stays below 90°C, the motor will not be damaged.
A surface temperature of 70–80°C is considered normal for a stepper motor and can be measured using an infrared thermometer. This level of heating will not affect the service life of the motor.
3. Solutions to Motor Overheating
3.1 Verify Driver Current Settings
Check whether the current setting on the driver is appropriate. If the current is set too high, reduce it to the minimum value that still meets your torque requirements. Also, enable the driver's half-current hold (reduced current hold) function to lower the current when the motor is stationary.
3.2 Check Driver Load and Temperature
Inspect the driver for signs of overload or overheating. If necessary, improve heat dissipation by adding a heatsink or cooling fan, or upgrade to a driver with a higher power rating.
3.3 Reduce Continuous Operating Time
If the stepper motor has been running continuously for an extended period, consider introducing rest intervals or adding forced-air cooling with a fan to reduce heat buildup.
3.4 Monitor Ambient Temperature
Check whether the ambient temperature around the motor is excessively high. If so, improve ventilation in the enclosure or lower the surrounding working temperature.
3.5 Inspect Power Cables and Connections
Inspect the power cables and all wiring connections for loose contacts, damaged wires, or undersized conductors. Excessive resistance in the cables can cause voltage drop and additional heat generation at the connection points, which may contribute to overall system overheating.