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The Relationship Between Step Angle and Subdivision of Stepper Motor

First, let us understand the concept of step angle: step angle is the corresponding angular displacement of the stepper motor rotor produced when an electrical pulse signal is input. It is related to the number of phases of the control winding, the number of rotor teeth and the mode of energization. The smaller the step angle, the better the smoothness of motor operation.

Common step angles are: 0.72°, 0.9°, 1.2°, 1.8°, 7.5°.
Generally, the step angle for two-phase motors is 0.9°/1.8°, for three-phase motors is 1.2°/1.5°, and for five-phase motors is 0.72°. In the absence of a subdivision driver, the user mainly relies on different phase numbers to meet his requirements for the step angle, and if a subdivision driver is used, then the number of phases becomes meaningless. Because the user only needs to change the subdivision number on the driver to change the motor's step angle.

Next, let's understand the concept of subdivision: before subdivision, the operation angle of the motor corresponding to each pulse is the whole step angle of the motor; after subdivision, the operation angle of each pulse is the whole step angle of the motor divided by the the subdivision number. For example, the basic step angle of a two-phase stepper motor is 1.8°, that is, one pulse makes the motor rotor produce an angular displacement of 1.8°, if there is no subdivision, it is 200 pulses to go around 360°.

The number of pulses required for the motor to run a lap after subdivision = 360 * the selected subdivision / motor step angle of the whole step.

Number of steps per turn = number of pulses required for one lap of motor operation after subdivision
Motor speed = pulse frequency * 60/subdivision n=(60f)/p

Example: If the input pulse frequency is 1000Hz, the subdivision gear of the driver is set to 2000 and the motor speed is 1000*60/2000=30rpm.

In the actual use of the motor, if the speed requirements are high and the accuracy and smoothness are not high, it is not necessary to choose high subdivision. If the speed is very low case, you should choose a large subdivision to ensure that the motor runs smoothly and vibration and noise are reduced.

Updated on: 09/04/2024

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