There are three main types of stepper motors in structure: reactive (Variable Reluctance, VR), permanent magnet (Permanent Magnet, PM) and hybrid (Hybrid Stepping, HS).
Reaction formula: There are windings on the stator and the rotor is composed of soft magnetic materials. The structure is simple, the cost is low, the step angle is small, up to 1.2°, but the dynamic performance is poor, the efficiency is low, the heat is large, and the reliability is difficult to guarantee.
Permanent magnet type: The rotor of the permanent magnet stepper motor is made of permanent magnet material, and the number of poles of the rotor is the same as the number of poles of the stator. It is characterized by good dynamic performance and large output torque. However, this motor has poor accuracy and large step angle (generally 7.5° or 15°).
Hybrid type: The hybrid stepper motor combines the advantages of the reactive type and the permanent magnet type. The stator has multi-phase windings and the rotor uses permanent magnet materials. There are multiple small magnets on both the rotor and the stator. teeth to improve step accuracy. It is characterized by large output torque, good dynamic performance, and small step angle, but has a complex structure and relatively high cost.
According to the winding on the stator, there are two-phase, three-phase and five-phase series. The most popular is the two-phase hybrid stepper motor, which accounts for more than 97% of the market share. The reason is that it is cost-effective and has good effects when coupled with a segmented driver. The basic step angle of this kind of motor is 1.8°/step. With a half-step driver, the step angle is reduced to 0.9°. With a subdivision driver, the step angle can be subdivided up to 256 times (0.007°/micro). step). Due to reasons such as friction and manufacturing accuracy, the actual control accuracy is slightly lower. The same stepper motor can be equipped with drivers of different subdivisions to change the accuracy and effect.