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Motor Knowledge Daquan: Analysis of stepper motor principle
- Jan 02, 2018 -

Stepper motor as the implementation of components, is one of the key products of mechanical and electrical integration, widely used in a variety of automated control systems. With the development of microelectronics and computer technology, the demand for stepper motors is increasing day by day, and has applications in various fields of national economy.


Stepper motor is a kind of electric pulse into angular displacement of the implementing agencies. When the stepper drive receives a pulse signal, it drives the stepping motor to rotate by a fixed angle (referred to as the "step angle") in the set direction, with its rotation running step by step at a fixed angle. By controlling the pulse number to control the angular displacement, so as to achieve the purpose of accurate positioning; the same time by controlling the pulse frequency to control the motor speed and acceleration of rotation, so as to achieve the purpose of speed. Stepping motor can be used as a special motor control, the use of its accumulated error (100% accuracy) features, widely used in various open-loop control.

Now more commonly used stepper motor, including reactive stepper motor (VR), permanent magnet stepper motor (PM), hybrid stepper motor (HB) and single-phase stepper motor.


Permanent magnet stepper motor is generally two-phase, smaller torque and size, step angle is generally 7.5 degrees or 15 degrees;

Reactive stepper motor is generally three-phase, enabling large torque output, step angle is generally 1.5 degrees, but the noise and vibration are great. Reactive stepper motor rotor magnetic circuit made of soft magnetic materials, the stator has a multi-phase excitation winding, the use of changes in the magnetic torque.


Hybrid stepping motor is the combination of permanent magnet and reactive advantages. It is divided into two phases and five phases: the two-phase step angle is generally 1.8 degrees and the five-phase step angle is generally 0.72 degrees. This stepper motor is the most widely used and is the stepper motor of the subdivision drive scheme.


Some basic parameters of the stepper motor:

Motor inherent step angle:

It indicates that each control system sends a step pulse signal, the angle of rotation of the motor. When the motor is delivered from the factory, a step angle value is given. For example, the 86BYG250A motor gives a value of 0.9 ° / 1.8 ° (0.9 ° for half-step operation and 1.8 ° for full-step operation). This step angle It can be called "motor inherent step angle", which is not necessarily the actual step angle when the motor is actually working. The true step angle is related to the driver.


Number of stepper motors:

Refers to the number of coils within the motor, the current commonly used two-phase, three-phase, four-phase, five-phase stepper motor. The motor phases are different and the step angle is also different. Generally, the step angle of the two-phase motor is 0.9 ° / 1.8 °, the three-phase is 0.75 ° / 1.5 ° and the five-phase is 0.36 ° / 0.72 °. In the absence of subdivision drive, the user mainly depends on the choice of different phases of the stepper motor to meet their own step angle requirements. If you use subdivided drives, then the number of phases becomes meaningless and the user can change the pitch angle simply by changing the number of subdivisions on the drive.



Refers to the stepper motor is energized but does not rotate, the stator lock rotor torque. It is one of the most important parameters of stepping motor, usually the torque of stepping motor at low speed approaches the holding torque. As the output torque of stepping motor decayed with the increase of speed, the output power also changes with the increase of speed, so holding torque becomes one of the most important parameters to measure stepping motor. For example, when people say that 2N.m stepper motor, in the case of special instructions is to maintain the torque of 2N.m stepper motor.



Refers to the stepper motor is not energized, the stator locked rotor torque.

DETENTTORQUE in the country there is no uniform translation, easy to make everyone misunderstood; due to the reactive stepper motor rotor is not a permanent magnet material, so it does not DETENTTORQUE.


Some features of stepper motor:

1. General stepper motor accuracy of 3-5% of the step angle, and does not accumulate.

2. Stepper motor allows the appearance of the highest temperature.

Stepper motor temperature is too high will first demagnetize the motor's magnetic material, resulting in torque down or even out of step, so the maximum allowable temperature of the motor surface should depend on the demagnetization of different motor magnetic materials; Generally, the demagnetization of magnetic materials Points are above 130 degrees Celsius, and some even as high as 200 degrees Celsius, so the stepping motor surface temperature 80-90 degrees Celsius is completely normal.

3. The torque of the stepper motor will decrease as the speed increases.

When the stepper motor rotates, the inductance of each phase winding of the motor will form a back electromotive force; the higher the frequency, the larger the back electromotive force. In its role, the motor with the frequency (or speed) increases and the phase current decreases, resulting in torque decline.

4. Stepping motor can operate normally at low speed, but if it is higher than a certain speed, it can not be started, accompanied by howling.

Stepper motor has a technical parameters: No-load starting frequency, that is, the stepper motor can normally start under no-load pulse frequency, if the pulse frequency is higher than this value, the motor can not start normally, may occur lost step or stalling. In the case of a load, the start frequency should be lower. If you want to make the motor reach high speed rotation, the pulse frequency should be accelerated, that is, the lower the starting frequency, and then at a certain acceleration to the desired high frequency (motor speed from low to high speed).

Stepper motor with its significant features, in the era of digital manufacturing plays a major purpose. With the development of different digital technologies and the advancement of stepping motor technology, stepper motors will be applied in more fields.


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