### Stepper Motor Selection Suggestion

- Aug 30, 2017-

Stepper Motor Selection Guide

Edit by Shenzhen ECON Technology Co.,Ltd

The stepper motor is special for control. Its rotation is run step by step at a fixed angle (called "step angle"), which is characterized by no accumulation error (100% accuracy) ，so widely used in various open-loop control.

The operation of the stepper motor is driven by an electronic device, which is stepper motor driver ,it converts the pulse signal from the control system into an angular displacement of the stepper motor, or to say: the control system sends a pulse signal,the drive on make the stepper motor rotate one step angle.So the speed of the stepper motor is proportional to the frequency of the pulse signal. Although the stepper motor has been widely used, it can not normal use as ordinary DC motor, AC motor. It must be used with control system which combined by double rings pulse signal, power drive circuit and other components. So it is not easy to use stepper motor, it involves the mechanical, motor, electronics and computer and other professional knowledge.

In order to allow more users to understand the stepper motor and stepper motor drive, select the most suitable stepper motor and stepper motor drive,so make stepper motor selection principle as follows: (for reference only)

1. First determine the torque required for the stepper motor to drag the load. The easiest way is to add a lever on the load shaft, pull the lever with a spring scale, pull force multiply arm length is the load torque. Or calculated theoretically according to load characteristics.  Due to step Motor is control motor, so current commonly used stepper motor maximum torque does not exceed 45Nm, the greater torque, the higher cost. If choose the motor torque is greater or beyond this range,can consider adding a reduction device.

2. Determine the maximum operating speed of the stepper motor. Speed is a very important indicator when select stepper motor, the characteristics of stepper motor is motor speed increases, the torque decreases, the decline of speed has relatives with a lot of parameters, such as: drive voltage,motor phase current, the phase inductance of the motor, the size of the motor, etc. The general rule is that the higher driving voltage, the slower the torque decreases; the greater of the motor phase current, the slower the torque decreases.At program design, the motor speed should be controlled at 1500 r / min or 1000 r / min, of course,can refer to <torque - frequency characteristics>

3. According to two important indicators:load maximum torque and the maximum speed, and refer to <torque - frequency characteristics>, can choose suitable stepper motor. If think choose a big motor, you can consider adding a reducer,which can save cost and make your design more flexible. To choose correct reduction ratio,consider torque and speed relationship.

4. Finally, consider a certain margin (such as 30%)of torque margin and speed margin.

5. Try to choose hybrid stepper motor, its performance is higher than the reflective stepper motor.

6. Try to select the micro-step drive and make the drive work in a micro-step state.

7. When select stepper motor,do not enter into such error zone: torque is the only one indicator,the greater torque,the better.Take speed and torque to be considered together.

8. In the case of high speed requirement can choose a higher voltage drive.

9. To choose two-phase or three-phase,do not have any specific requirements, as long as the step angle can meet the using requirements.