The rotor of the screw stepper motor is a permanent magnet. When current flows through the stator winding, the stator winding generates a vector magnetic field. The magnetic field will drive the rotor to rotate an angle, so that the direction of the pair of magnetic fields of the rotor is consistent with the direction of the magnetic field of the stator. When the stator’s vector magnetic field rotates by an angle. The rotor also turns an angle with the magnetic field. Each time an electric pulse is input, the motor rotates an angle to advance. The angular displacement of the screw stepper motor output is proportional to the number of pulses input, and the speed is proportional to the pulse frequency. Change the winding energization sequence, the motor will reverse. Therefore, the rotation of the stepper motor can be controlled by controlling the number of pulses, the frequency and the energizing sequence of each phase winding of the motor.
The various types of motors commonly seen in the heating principle of screw stepper motors have iron cores and winding coils inside. There is resistance in the winding, and loss will occur when energized. The loss is proportional to the resistance and the square of the current. This is the copper loss we often say. If the current is not a standard DC or sine wave, harmonic loss will also occur; the core has hysteresis eddy current effect, and it also produce losses in the alternating magnetic field, its size is related to the material, current, frequency, voltage, which is called iron loss. Both copper loss and iron loss will be expressed in the form of heat, which affects the efficiency of the motor. Screw stepper motors generally pursue positioning accuracy and torque output. The efficiency is relatively low, the current is generally large, and the harmonic content is high. The frequency of the alternating current also changes with the speed. Therefore, the stepper motor generally has a heating situation, and the situation is more serious than normal AC motor.
The screw stepper has advantages of high precision, easy control, low noise,which is suitable for high precision instruments, robot vacuum cleaners and robots.