Articles on: Trouble Shooting

Reasons for Stepper Motor Shaft Lock When Not Powered On

When the power is off, the reason why the stepper motor locks its shaft may be that the two wires of the same set of coils are short-circuited.

First, we need to understand the working principle of stepper motors. Stepper motors are composed of iron cores, coils, etc. The rotor inside the stepper motor is a permanent magnet with polarity (which can be understood as a strong magnet), and several sets of coils are embedded in the stator. When we pass a current in a certain direction through some coils of the stator, a magnetic field with a certain direction will be formed inside the stator.

Under the action of this magnetic field, the permanent magnet stator will be positioned according to the principle of attraction between the N pole and the S pole (the principle of minimum magnetic resistance). As long as we change the current size and direction of the external coil to make the magnetic field generated by the stator rotate in a certain direction and speed, we can make the rotor rotate with the magnetic field of the stator.





The permanent magnet of the rotor and the stator coil generate magnetic lines of force. When the motor is not powered, the rotor rotates, and the stator coil cuts the magnetic lines of force of the rotor to generate current.

If the two wires of the same set of coils are short-circuited at this time, the rotation of the motor shaft will become quite difficult due to the large induced current generated by the induced electromotive force during rotation, which hinders the rotation. This will cause the shaft to lock.

Updated on: 29/11/2024

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