For all kinds of stepper motors, the interior of stepper motor is composed of iron core and winding coil. If the winding has resistance, power on will produce loss, and the loss is directly proportional to the square of resistance and current, which is what we often call copper loss. If the current is not standard DC or sine wave, it will also produce harmonic loss; The iron core has hysteresis eddy current effect and will also produce loss in alternating magnetic field. Its size is related to material, current, frequency and voltage, which is called iron loss. Copper loss and iron loss will be expressed in the form of heating, which will affect the efficiency of the motor. Stepper motors generally pursue positioning accuracy and torque output, with low efficiency, large current, high harmonic component, and the frequency of current alternating also changes with speed. Therefore, stepper motors generally have heating, which is more serious than ordinary AC motors.