Stepper Motor | Construction, Working and Types

Sunday, November 13, 2011 , No comments

Stepper Motor
Stepper Motor - Construction and Working

A stepper Motor is basically a synchronous Motor. In stepper motor there is no brushes. This motor does not rotate continuously, instead it rotates in form of pluses or in discrete steps. Thats why it is called stepper motor. There are different types of motors available on the basis of steps per rotation, for example- 12 steps per rotation, 24 steps per rotation etc. We can control or operate Stepper motor with the feedback or without any feedback. A simple image of stepper motor is shown in above picture.
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Working Principle Of Stepper Motor:

The principle of Working of stepper motor is Electro-Magnetism. It constructs of a rotor that is of permanent magnet and a stator that is of electromagnets  The following figure shows the construction of a practical stepper motor:


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Now when we gives supply to stator's winding. There will be a magnetic field developed in the stator. Now rotor of motor that is made up of permanent magnet, will try to move with the revolving magnetic field of stator. This is the basic principle of working of stepper motor. Now we are going to discuss its types. In this note you will find the real method of working of specific type of servo motor.

Types of Servo Motor:

The Stepper Motor is of following types:
  • Permanent Magnet
  • Variable Reluctance.
  • Hybrid Stepper Motor
The first type is most important, so first we should discuss it.

Permanent Magnet Type Stepper Motor:
 The Working and Construction of the Permanent Magnet Type Stepper Motor is given below:
The permanent magnet type stepper motor has a stator, that is of electromagnets and a rotor that is of Permanent Magnet, therefore this motor is called permanent magnet type stepper motor.
Working:
When we gives supply to the stator, the winding of stator is energized and hence produces magnetic field. As described above, the rotor is made up of permanent magnet, thats why it tends to follow the revolving field. Thus an stepper motor works.
The speed or torque of a permanent magnet type motor is changed by the number of poles used in stator, If we use a large number of poles in stator then the speed of motor will increase and if we use a less number of poles then the speed will decrease.
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The diagram of Permanent Magnet Type Stepper Motor is given below:

Variable Reluctance Motor:  

In Variable reluctance stepper motor, we uses a non magnetic iron core rotor, which has winding turned on its surface. The stator is same as used in the Permanent Type Stepper Motor. 
Working:
When we apply supply to the stator, a magnetic field is induced in the stator winding which causes an e.m.f. induction in the rotor's winding, thus a magnetic field is also set up in the rotor which tends to follow the magnetic field of stator. 
The diagram of Variable reluctance stepper motor is given below:
The speed control method is almost same as in the permanent magnet type motor. In this motor we can increase the speed by increasing the number of poles of stator as well as by increasing the number of teeth of rotor and vice versa.
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Hybrid Type Stepper Motor:
The Hybrid type motor, as the name suggests is a mixture of both above types. This consists a rotor which is magnetic and as well as teethed. The diagram of the construction of this motor is shown below:
The rotor of this type of motor is made up of two rotors joining like a shaft of motor. One of them is for north and other is for south pole. These poles arrange in alternative manner as they designed in such a manner.

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