The stepper motor is a brushless DC motor. Control signals are applied to the stepper motor to incrementally rotate it. Its speed of rotation depends on the speed at which the control signals are applied. Several stepper motors are available with a minimum required step angle. consists mainly of two parts, a stator and a rotor. The stator is wound and the rotor is mainly made of a permanent magnet or ferromagnetic material.

 Stepper Motor
Stepper Motor

Inside a  of Stepper Motor

 Stepper Motor parts
Stepper Motor parts

Working of Stepper Motor

The construction of a stepper motor is very similar to that of a DC motor, it contains a permanent magnet as a rotor, which is located in the middle and rotates when a force is applied. of the stator, which is wound all around by a magnetic coil. The stator is arranged close to the rotor so that the magnetic fields within the stators can control the movement of the rotor.

The stepper motors can be controlled by supplying power to each stator individually. So the stator is magnetized and acts as an electromagnetic pole that uses the repulsive energy in the rotor to move forward. convert it through great control.

The working principle of stepper motors is electromagnetism. It contains a rotor made with a permanent magnet while a stator is made with electromagnets. As soon as the stator winding is supplied, the magnetic field develops inside the stator. in the motor begins to move with the rotating magnetic field of the stator. This is the basic working principle of the stepper motor.

Inside this motor there is a soft iron enclosed by the electromagnetic stators, the poles of the stator and rotor do not depend on the type of stepper motors, when power is supplied to the stators of this motor, the rotor will rotate. align with the stator, otherwise it will rotate to have the least amount of clearance through the stator. This activates the stators in series to rotate the stepper motor.

Unipolar Stepper Motor and Bipolar Stepper Motor 

  1. Unipolar :The unipolar stepper motors has a centre winding with 5 (if both centers are connected internally) or 6 wires as shown in the following figure. As a rule, these central connections are connected to the power supply. By providing a ground path to the winding leads, we can allow current to flow through each half of the coil, creating magnetic poles. By sequentially changing the poles, we can turn the rotor accordingly. In the unipolar motor, the current is the unidirectional center tap, each winding is divided i. The current flows through the center of the winding, and because of the location of the center tap, we do not have to change the direction of the current to change the magnetic pole in the winding. Here we just need to change the ground connection at the ends of the winding.
  2. Bipolar:The bipolar stepper motors has no center tap. Usually there are two turns of 4 ends of the cable, as shown in the following figure. Current flows through the entire stator winding. In the bipolar stepper motor i the current is bidirectional. We have to change the direction of the current. through the winding to change the magnetic pole of that winding.

Difference Between Unipolar and Bipolar motor

According to their name, they already differ in the direction of the current. In addition, the unipolar stepper motor does not require any control of the current direction due to the unidirectional arrangement. It, therefore, does not require an H-bridge type circuit for bidirectional operation. A simple ULN2003 driver circuit is used to drive it. A He bridge driver circuit is required for a bipolar stepper motor. like the L293D controller for bidirectional current control. The unipolar stepper motors has a lower torque than the bipolar stepper motors because with the unipolar stepper motor the current flows through the centre of the winding; while with the bipolar stepper motors the current flows through the complete winding

Permanent Magnet Stepper Motor

Permanent Magnet Stepper MotorS

It is an electromechanical energy conversion device that converts electrical energy into mechanical energy. With stepper motors, the magnetic fields of the rotor and stator are excited in such a way that the interaction between the rotor magnetic field and the stator magnetic field generates torque. With permanent magnet stepper motors, the rotor coils are not excited, instead, we use permanent magnets, with conventional stepper motors electromagnets are used to generate a magnetic field from the rotor that needs to be excited externally, but in this case, we are using permanent magnets. It reduces the excitation system of the rotor and makes the engine more compatible with the operation. The lack of rotor excitation also reduces losses.

Variable Reluctance Stepper Motor

A non-magnetic iron core is used as the rotor. The stator is an electromagnetic winding around the rotor. The rotor consists of teeth. These teeth are attracted to the energized winding when a magnetic path is created around the coil and rotor. The rotor experiences a torque and is aligned with the energized coil to minimize flux. If the next winding is now energized, the rotor moves towards it.

In this way the continuous pulse train of the winding causes the rotor to rotate continuously. Note that the rotor teeth are arranged so that only one rotor tooth is energized and the pair of winding coils are aligned, while other teeth differ slightly with different windings. As shown in the figure below, the energized winding C is aligned with the rotor teeth.

Variable Reluctance Stepper Motor

The stepper motors with variable reluctance is based on the property of flux lines that detect the low-resistance path. The stator and rotor of the motor are aligned so that the magnetic reluctance is minimal.

Hybrid Stepper Motor

Hybrid Stepper Motor
Hybrid Stepper Motor

Hybrid motors are a combination of permanent magnet and a stepper motors with variable reluctance. The permanent magnet inside the rotor and iron core outside the rotor. The permanent magnet forms the north and south poles on the rotor. It has two rotor shells, as shown in the picture, which is made of permanent magnet teeth. Notice that your teeth are arranged in a zigzag. Hybrid stepper motors have higher torque and can achieve a smaller step size.

How to Rotate Stepper Motor

It rotates incrementally and for continuous or limited angular rotation we need to provide sequential steps. Most of the time there are two sequences of steps that are used to rotate the stepper motor as shown in figure I below.

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Amith G Nair
Experience as a product developer, innovation coach, and electronics lecturer,a seasoned professional driven by passion for designing projects.expertise extends to 3D modelling, hardware designing, and web development using HTML, WordPress, and Django.