What Is Stepper Motor, Working Principle, Types, Advantages, Disadvantages

Hello guys, welcome back to my blog. In this article, I will discuss what is the stepper motor, working principle. types, advantages, disadvantages. Means working principle of the stepper motor, types of the stepper motor, advantages of the stepper motor, disadvantages of the stepper motor, etc.

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What Is Stepper Motor, Working Principle, Types, Advantages, Disadvantages


What Is Stepper Motor

Introduction


  1. This is the special type of DC motor, that converts input digital Pulses into mechanical shaft rotation.
  2. It converts a train of Input pulses (square wave pulses ) into precisely defined increment in the shaft position.
  3. Every pulse of a square wave moves the shaft of the stepper motor through a fixed angle so we can defined stepper motor as, “ This is as electrochemical which actuates train of step movements of a shaft with with respect to the train of input pulses.“  
  4. The movement of the step may be angular or linear. There will be a one-one relation between input pulses And step movement.
  5. Each and every pulse which is supplied to the motor as input actuates one step movement of the shaft.
  6. The shaft rotates at some angle. The angle at which shaft rotates for every pulse is known as the step angle. That will be expressed in degrees. E.g.( 7.5° ). This angle will depend on the number of square wave pulses. This type of system is used to control the position. That’s why this is also called a position control system. 
  7. The average speed of the motor is directly proportional to the rate at which the input pulse is delivered. If the rate is low, then the motor rotates in steps. If the rate of pulses is high, then the motor rotates smoothly like DC motors. This is due to wear and tear i.e. Friction. Due to this property stepper motor can also be used in speed control systems.
  8. The stepper motors are manufactured with the steps of 12,24,72,144,180,200 with the angle of 30, 15, 5, 2.5, 2, 1.8.
  9. We can operate a stepper motor with or without feedback control.

Working Principle Of Stepper Motor


Working Principle Of Stepper Motor

  1. The stepper motor works on the principle of Electromagnetism. It consists of two main parts i.e., Rotor and Stator. 
  2. For rotor, we can use a permanent magnet or soft iron and the rotor part will be surrounded by electromagnetic stators.
  3. If we give a voltage at terminals, the rotor tries to align with the stator. To maintain a minimum gap with the stator which is due to magnetic effect.
Here I would like to take a stepper motor which consists of 4 pole rotor construction. i.e. rotor is having 4 salient poles without any exciting winding.


Stages In Stepper Motor

Stages In Stepper Motor



When we excite AA' phase by keeping SW1 switch as close, then stator magnetic axis align along the poles formed due to AA' ( vertical ). Then the rotor tries to adjust itself in a minimum reluctance position i.e. matching its own axis which passes through the two poles exactly with the stator magnetic axis. 

Then next when we excite phase BB' by keeping SW2 switch off and AA' phase de-energized by keeping SW1 switch open. Now the stator magnetic axis shifts towards the pole which is formed by BB'. Then again rotor tries to align in minimum reluctance & it will turn by a 30° step angle in an anti-clockwise direction. The axis passing along two diagonally opposite poles of the rotor will match with the stator magnetic axis. The point P will be the new position of minimum reluctance.

Then next when we excite phase CC' by keeping SW3 switch off and AA' and BB' phases are de-energized by keeping SW1 & SW2 switches open. Now the stator magnetic axis shifts towards the poles formed due to CC'. Then rotor tries to align in minimum reluctance & it will turn by 60° step angle in an anti-clockwise direction.

After exciting the three phases, the motor takes 12 steps to complete one full revolution.

 Types Of Stepper Motor


  1. Variable reluctance stepper motor.
  2. Permanent magnet stepper motors.
  3. Hybrid stepper motors. 

Comparison between the variable reluctance stepper motor and permanent magnet stepper motor


Variable reluctance motor

  1. The rotor part is not magnetized.
  2. The step angle is small.
  3. It will not be having detent torque.
  4. Salient rotor.
  5. A dynamic response will be faster.
  6. The acceleration rate will be high.
  7. Torque inertia ratio is low.

Permanent magnet stepper motor

  1. Having a magnetized rotor part.
  2. Step angles are of range 30 to 90 degrees.
  3. It will be having detent torque.
  4. Cylindrical rotor.
  5. A dynamic response will be slow.
  6. The acceleration rate will be slow.
  7. Torque inertia ratio is high.

Advantages And Applications Of The Stepper Motor

  1. Used in X-Y plotters.
  2. It is used in a floppy disk drive.
  3. In machine tools. 
  4. Used in the process control system. 
  5. Also, used in robotics. 
  6. It is used in printers. 
  7. Used in tape drives and a variety of other industrial applications.

Disadvantages Of Stepper Motor

  1. It’s having low efficiency.
  2. Torque drops rapidly with speed.
  3. Having low output power for size.
  4. Missing of feedbacks to indicate missed steps.
  5. Heat experience in high-performance configurations.
  6. Low accuracy at full load.
I hope this article may help you all a lot. Thank you for reading. 

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