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# How To Select Stepper Motor And Its Basic Principle

Jan 11, 2020

## Select method

### Stepper motor and driver selection method:

Judge how much torque is needed: static torque is one of the main parameters to choose stepper motor. When the load is large, large torque motor should be used. When the torque index is large, the motor shape is also large.

Judge the motor running speed: when the speed requirement is high, the motor with larger phase current and smaller inductance should be selected to increase the power input. The driver is selected at a higher power supply voltage.

Select motor installation specifications: 57, 86, 110, etc., mainly related to torque requirements.

Determine positioning accuracy and vibration requirements: determine whether and how many subdivisions are required.

Select the driver based on the motor's current, subdivision, and supply voltage.

## Stepper Motor Basic Principle

### Working Principle

Usually the rotor of the motor is a permanent magnet. When the current flows through the stator windings, the stator windings produce a vector magnetic field. The magnetic field will cause the rotor to rotate by an Angle, so that the direction of the rotor's magnetic field is the same as that of the stator's magnetic field. When the stator's vector magnetic field rotates by an Angle. The rotor also rotates at an Angle with the magnetic field. For each input of an electrical pulse, the motor rotates at an Angle one step further. The output angular displacement is proportional to the number of pulses and the speed is proportional to the pulse frequency. Change the order in which the windings are energized and the motor reverses. Therefore, the rotation of the stepper motor can be controlled by controlling the number of pulses, frequency and the power-on sequence of each phase winding of the motor.

### Heating Principle

Usually see all kinds of motor, the internal are iron core and winding coils. Winding has resistance, electrifying will produce loss, loss size is proportional to the square of resistance and current, this is what we often say copper loss, if the current is not the standard dc or sine wave, will also produce harmonic loss; Core has hysteresis eddy current effect, in the alternating magnetic field will also produce losses, the size of the material, current, frequency, voltage, this is called iron loss. Copper and iron losses will be in the form of heat, thus affecting the efficiency of the motor. Stepper motors generally pursue positioning accuracy and torque output, with low efficiency, large current and high harmonic components, and the frequency of alternating current also changes with the speed, so stepper motors generally have heating conditions, and the situation is more serious than the general ac motor.