What is the Principle of Screw Stepper Motors?

Every motor converts power. Electric motors convert electricity into motion. Stepper motors convert electricity into rotation. Not only does a stepper motor convert electrical power into rotation, but it can be very accurately controlled in terms of how far it will rotate and how fast.

 

Micro stepper motors are often divided into three types: permanent magnet stepper motor (PM), variable reluctance stepper motor (VR) and hybrid stepper motor (HB). No matter which kind of stepper motors, they have a stationary part (the stator) and a moving part (the rotor).

Here we take a typical type, permanent magnet stepper motor, as an example. 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 turns an angle with the magnetic field. An electric pulse at each time is the 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 contain 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, the harmonic loss will also occur; the core has a hysteresis eddy current effect, and it also produces losses in the alternating magnetic field. Such losses are called iron losses which are related to the material, current, frequency and voltage. Both copper loss and iron loss will be expressed in the form of heat, which affects motor efficiency. 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 generates heat during the operation. But now some manufacturers like ZHAOWEI focus on relying on technology to improve the reliability of the product with advantages of high precision, easy control and low noise, which is suitable for high precision instruments, electric curtains, and robots.