Stepper motors, as digital actuators, are widely used in motion control systems. Many users notice that stepper motors get quite hot during operation, causing concern about whether this is normal. In fact, heat generation is a common phenomenon with stepper motors, but what level of heat is considered normal, and how can we minimize stepper motor heat generation? This article will provide a simple analysis of these questions. 1. Why Do Stepper Motors Get Hot? All stepper motors consist internally of an iron core and winding coils. The windings have resistance, and when current flows through them, losses occur. The magnitude of these losses is proportional to the resistance and the square of the current; this is what we commonly call copper loss. If the current is not standard DC or a sine wave, harmonic losses will also occur. The iron core has hysteresis and eddy current effects, which also generate losses in an alternating magnetic field. The magnitude of these losses depends on the material, current, frequency, and voltage; this is called iron loss. Both copper and iron losses manifest as heat, thus affecting the motor's efficiency. Stepper motors generally prioritize positioning accuracy and torque output, resulting in relatively low efficiency, high current consumption, and high harmonic content. The frequency of the alternating current also varies with the rotational speed. Consequently, stepper motors commonly experience heat generation, often more severely than typical AC motors. 2. The reasonable range of stepper motor heat generation: The permissible level of heat generation depends primarily on the motor's internal insulation level. Internal insulation performance is only compromised at high temperatures (above 130 degrees Celsius). Therefore, as long as the internal temperature does not exceed 130 degrees Celsius, the motor will not be damaged, and the surface temperature will be below 90 degrees Celsius. Thus, a surface temperature of 70-80 degrees Celsius is normal for a stepper motor. A simple temperature measurement method using a spot thermometer can provide a rough estimate: if you can touch it for more than 1-2 seconds, it's below 60 degrees Celsius; if you can only touch it briefly, it's approximately 70-80 degrees Celsius; if a few drops of water vaporize quickly, it's above 90 degrees Celsius. 3. Stepper motor heat generation changes with speed: When using constant current drive technology, the current in a stepper motor remains relatively constant under static and low-speed conditions to maintain constant torque output. At high speeds, the back electromotive force inside the motor increases, the current gradually decreases, and the torque also decreases. Therefore, the heat generated by copper losses is speed-dependent. Generally, heat generation is high at static and low speeds, and low at high speeds. However, the change in iron losses (although they account for a smaller proportion) is not always consistent, and the total heat generation of the motor is the sum of both. Therefore, the above is only a general observation. 4. Impact of Heat Generation: While motor heat generation generally does not affect the motor's lifespan and is unnecessary for most customers, severe heat generation can have some negative effects. For example, differences in the thermal expansion coefficients of different parts of the motor can lead to changes in structural stress and slight changes in the internal air gap, affecting the motor's dynamic response and making it prone to loss of synchronization at high speeds. Furthermore, excessive motor heat generation is unacceptable in some applications, such as medical devices and high-precision testing equipment. Therefore, necessary control of motor heat generation is essential. 5. How to Reduce Motor Heat Generation: Reducing heat generation means reducing copper and iron losses. Reducing copper losses has two aspects: reducing resistance and current. This requires selecting motors with low resistance and low rated current during the selection process. For two-phase motors, series connection should be used whenever possible instead of parallel connection. However, this often conflicts with torque and high-speed requirements. For a selected motor, the automatic half-current control and offline functions of the driver should be fully utilized. The former automatically reduces current when the motor is static, and the latter simply cuts off the current. In addition, microstepping drivers have a near-sinusoidal current waveform with fewer harmonics, resulting in less motor heat generation. There are few ways to reduce iron losses, and voltage level is related. While high-voltage drives improve high-speed characteristics, they also increase heat generation. Therefore, an appropriate drive voltage level should be selected, balancing high speed, smoothness, heat generation, and noise levels.