How is the stepper motor model composed?

The stepper motor model consists of 4 parts, which represent the frame number, motor type (BYF represents hybrid type, BC represents reactive type), number of phases, and number of motor rotor teeth.

1. Frame number: also called motor outer diameter, there are 28, 42, 57, 86, 110, and 130 models.

2. Motor type
Reactive type: There are windings on the stator and the rotor is made of soft magnetic material. It has a simple structure, low cost, small step angle, up to 1.2°, but poor dynamic performance, low efficiency, high heat generation, and difficult reliability.

Permanent magnet type: The rotor of the permanent magnet stepper motor is made of permanent magnet material, and the number of rotor poles is the same as the number of stator poles. It is characterized by good dynamic performance and large output torque, but this motor has poor accuracy and a large step angle (generally 7.5° or 15°).

Hybrid: The hybrid stepper motor combines the advantages of the reactive and permanent magnet types. It has multi-phase windings on the stator, permanent magnet materials on the rotor, and multiple small teeth on the rotor and stator to improve the step accuracy. Its characteristics are large output torque, good dynamic performance, and small step angle, but the structure is complex and the cost is relatively high.

3. Number of phases: the number of excitation coils that produce different polar N and S magnetic fields. It is usually represented by m.

4. Number of rotor teeth

The number of rotor teeth is the number of rotor teeth on the specified rotor core. The difference in the number of rotor teeth will change the complementarity between the single-phase coils; change the polarity of the magnetic flux of the coil, affect the harmonic components of the magnetic flux of the single-phase coil, and then affect the harmonic characteristics of the motor, and also affect the power density of the motor.

Stepper motors are composed of three major elements: step angle (involving the number of phases), static torque, and current. Once the three major elements are determined, the model of the stepper motor is determined.

1. Step angle selection

The step angle of the motor depends on the load accuracy requirements. The minimum resolution (equivalent) of the load is converted to the motor shaft. How many angles should each equivalent motor move (including deceleration). The step angle of the motor should be equal to or less than this angle.

2. Static torque selection

The basis for static torque selection is the load of the motor, and the load can be divided into two types: inertial load and friction load. Single inertial load and single friction load do not exist. When starting directly (generally at low speed), both loads must be considered. When accelerating to start, the inertial load is mainly considered. When running at a constant speed, only the friction load needs to be considered.

3. Current selection

Motors with the same static torque have very different operating characteristics due to different current parameters. The current of the motor can be judged based on the torque-frequency characteristic curve.