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An article lets you understand stepper motors

Views: 12     Author: Site Editor     Publish Time: 2023-05-22      Origin: Site


Stepping motor, also known as pulse motor, is a kind of induction motor, which involves many professional knowledge such as machinery, motor, electronics and computer. As an actuator, the stepper motor is one of the key products of mechatronics and is widely used in various automation control systems. With the development of microelectronics and computer technology, the demand for stepper motors is increasing day by day, and they are used in various national economic fields.

What is a stepper motor

A stepper motor is an actuator that converts electrical pulses into angular displacement. It converts electrical pulse signals into angular displacement or linear displacement, and is the main actuator in modern digital program control systems, and is widely used.

The stepper motor control system consists of three parts: stepper motor controller, stepper motor driver, and stepper motor. The stepper motor controller is the command center, which sends signal pulses to the stepper motor driver, and the stepper motor driver receives When the signal pulse is converted into an electric pulse, the stepper motor is driven to rotate. Every time the controller sends out a signal pulse, the stepper motor rotates by an angle, and its rotation runs step by step at a fixed angle. The controller can control the rotation angle of the stepper motor by controlling the number of pulses, so as to achieve accurate positioning. The rotation speed of the stepper motor is precisely controlled by controlling the pulse frequency.

The structure and working principle of stepper motor

Usually the rotor of the motor is a permanent magnet. When the current flows through the stator winding, the stator winding generates a vector magnetic field. The magnetic field will drive the rotor to rotate at an angle, so that the direction of a 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 an angle. The rotor also turns an angle with this magnetic field.

Each time an electric pulse is input, the motor rotates an angle and advances one step. The angular displacement it outputs is proportional to the number of input pulses, and the rotational speed is proportional to the pulse frequency. Change the order in which the windings are energized, and the motor will reverse. Therefore, the rotation of the stepper motor can be controlled by controlling the number of pulses, frequency and the energization sequence of each phase winding of the motor.

The principle of stepper motor

When the stepper motor switches the excitation current of the stator winding once, the rotor rotates at a fixed angle, which we call the step angle. The step angle is generally obtained by the rotational torque generated by the switched phase current, so the number of poles per phase needs to be even. Stepper motors are usually more than two phases, and of course there are some special single-phase stepper motors with only one coil. Although it is single-phase, it is actually the direction of the magnetic flux generated by a coil that reverses alternately to drive the rotor to rotate. Of course, in our actual operation, the number of phases of the practical stepper motor is single-phase, two-phase, three-phase, four-phase, and five-phase.

Factors that determine the stepper motor angle

The higher the stepper motor resolution (number of steps per revolution, 360° divided by the step angle), the higher the position accuracy. In order to obtain high resolution, the number of poles should be designed more. The PM-type rotor has N and S poles alternately placed on the outer surface of the rotor core at equal intervals. The number of rotor poles is the sum of the number of N poles and S poles. To simplify the explanation, the number of pole pairs is assumed to be 1. Here, it is determined that the step angle θs of the stepper motor whose rotor is a permanent magnet is expressed by the following formula, where Nr is the number of rotor pole pairs, P is the number of stator phases,


The physical meaning of the above formula is as follows:The mechanical angle for one revolution of the rotor is 360°. , If the pole number 2Nr is used to remove it, it is equivalent to the mechanical angle occupied by one pole, which is 180°/Nr. That is to say, the mechanical angle of a pole is divided by the number of stator phases to obtain the step angle. This concept is shown in the figure below.

From the formula θs=180°/PNr, it can be seen that the smaller the step angle, the higher the resolution, so to improve the resolution of the stepping motor, it is necessary to increase the number of rotor pole pairs or use a multi-phase formula with more stator phases P method. However, the increase of Nr is limited by machining, so to manufacture a high-resolution stepping motor, two methods must be used together.

Classification of stepper motor

The best stepper motor will be capable of delivering your required torque while also being fast enough.I tell you my best picks depending on the category of the stepper motor:

Video of Stepper motor


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