The stepping motor is composed of three major factors: the step angle (involving the number of phases), the static torque, and the current. The three major factors are determined, and the model of the stepper motor is determined.
、步距角的选择 1.Selection of step angle
The step angle of the motor depends on the requirements of the load accuracy. The minimum resolution (equivalent) of the load is converted to the motor shaft. How many angles (including deceleration) should each motor travel. The step angle of the motor should be equal to or less than this angle. 0.36 度 /0.72 度（五相电机）、 0.9 度 /1.8 度（二、四相电机）、 1.5 度 /3 度（三相电机）等。 The step angles of stepper motors on the market are generally 0.36 degrees / 0.72 degrees (five-phase motors), 0.9 degrees / 1.8 degrees (two- and four-phase motors), and 1.5 degrees / 3 degrees (three-phase motors).
、静力矩的选择 2.Selection of static moment
The dynamic torque of a stepper motor is difficult to determine at once, we often determine the static torque of the motor first. The choice of static torque is based on the load of the motor, and the load can be divided into inertia load and friction load. There is no single inertial load or single friction load. When starting directly (usually at low speed), both loads must be considered. When accelerating starting, inertia loads are mainly considered. For constant speed operation, only friction loads need to be considered. 2-3 倍内好，静力矩一旦选定，电机的机座及长度便能确定下来（几何尺寸）。 In general, the static torque should be within 2-3 times of the friction load. Once the static torque is selected, the motor base and length can be determined (geometric size).
、电流的选择 3 , the choice of current
Motors with the same static torque have different running characteristics due to different current parameters. You can judge the motor current based on the torque-frequency characteristic curve.
Driving methods and requirements
The stepper motor cannot be directly connected to the power frequency AC or DC power supply to work, but must use a dedicated stepper motor driver, which is composed of a pulse generation control unit, a power drive unit, a protection unit and so on. The drive unit is directly coupled to the stepper motor, which can also be understood as the power interface of the stepper motor microcomputer controller.
、能够提供较快的电流上升和下降速度，使电流波形尽量接近矩形。 1. It can provide fast current rising and falling speed, so that the current waveform is as close to a rectangle as possible.
It has a circuit for releasing the current flow during the cut-off period to reduce the back electromotive force at both ends of the winding and accelerate the current attenuation.
、具有较高韵功率及效率。 2. It has high rhyme power and efficiency.
Stepper motor driver, which converts the pulse signal sent by the control system into the angular displacement of the stepper motor, or that is: each time the control system sends a pulse signal, the stepper motor is rotated by a step angle through the driver. In other words, the speed of the stepping motor is proportional to the frequency of the pulse signal. Therefore, controlling the frequency of the step pulse signal can accurately adjust the speed of the motor; controlling the number of step pulses can accurately position the motor. There are many stepper motor drivers, which should be reasonably selected based on actual power requirements.