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What is the stepper motor?

Visit: -Release time: 2017-06-12 15:25:00
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The stepper motor is a special motor that is specifically designed for precise position and speed control. The biggest characteristic of the stepper motor is its "digital", and for each pulse signal from the controller, the stepper motor operates at a fixed angle (referred to as a step) as driven by its drive, as shown in the following figure. Such as receiving a string of pulse stepper motor will continue to run a corresponding distance. At the same time by controlling the pulse frequency, directly to the motor speed control. As the principle of stepper motor easy to learn and use, low cost (relative to the servo), motor and drive is not easy to damage, very suitable for microcomputer and microcontroller control, so in recent years in all walks of life control equipment to obtain more and more widely application.
Types and characteristics of stepper motors
Stepper motors have three main types of construction: Variable Reluctance (VR), Permanent Magnet (PM) and Hybrid (Stepping, HS).
Reaction type
The stator has a winding, the rotor is composed of soft magnetic material. Simple structure, low cost, small step angle, up to 1.2 °, but the dynamic performance is poor, low efficiency, heat, reliability is difficult to guarantee.
Permanent magnet type
The rotor of the permanent magnet type stepping motor is made of permanent magnet material with the number of poles of the rotor being the same as the number of poles of the stator. It is characterized by good dynamic performance, large output torque, but the motor accuracy is poor, step angle angle (usually 7.5 ° or 15 °).
mixed type
Hybrid stepper motor combines the advantages of reactive and permanent magnet, the stator has a multi-phase winding, the rotor using permanent magnet material, the rotor and the stator have a number of small teeth to improve the accuracy of the steps. It is characterized by large output torque, dynamic performance, small step angle, but the structure is complex, the cost is relatively high.
According to the stator winding to the points, a total of two-phase, three-phase and five-phase series. The most popular is the two-phase hybrid stepper motor, accounting for more than 97% of the market share, the reason is cost-effective, coupled with the breakdown of the drive after the effect is good. The basic step angle of the motor is 1.8 ° / step, with the half step driver, the step angle is reduced to 0.9 °, with subdivision drive after the step angle can be subdivided up to 256 times (0.007 ° / micro step). Due to friction and manufacturing accuracy and other reasons, the actual control accuracy is slightly lower. The same stepper motor can be equipped with different segments of the drive to change the accuracy and effectiveness.
How to choose stepper motor and drive
To determine how much torque: static torque is to choose one of the main parameters of stepper motor. Large load, the need to use large torque motor. When the torque index is large, the motor shape is also large.
Judge the motor speed: high speed requirements should be selected when the current is larger, the inductance of the smaller motor to increase the power input. And a higher supply voltage is used when the driver is selected.
Select the motor installation specifications: such as 57,86,110, etc., mainly related to the torque requirements.
Determine the positioning accuracy and vibration requirements: to determine whether the need to break down, how much subdivision.
Select the drive according to the motor current, subdivision and supply voltage.

Keywords in the article: Brush Motor   Brushless motor   DC motor   Motor manufacturers

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