STEPPER MOTOR AND ITS TYPES


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                   **STEPPER MOTOR AND ITS TYPES**

A stepper motor is an electromechanical device which does the conversion of the electric pulse to discrete mechanical movements every revolution of the stepper motor is divided into a discrete number of steps and the motor must be sent separate pulse for each step. The shaft of the stepper motor rotates in discrete step increments when the proper sequence of the electrical commands are applied to it

Motor rotation has many relationships with these applied pulses, motor shaft rotation is directly related to the sequence of the applied pulse and the speed of the shaft rotation is directly related to the frequency of the input pulse, and then the length of the rotation is directly related to the number of applied input pulse with a computer controlled stepping we can achieve very precise positioning and speed control and for this reason stepper motor is used for many precision motion control applications. Stepper motor has many different sizes and electrical characteristics.

TYPES OF STEPPER MOTOR

There are three types of stepper motor they are

  • Variable-Reluctance
  • Permanent magnet
  • Hybrid

VARIABLE RELUCTANCE

This type of motor has a soft iron multi-toothed rotor and a wound stator the poles will be magnetized when the stator winding is energized with the DC current when the rotor teeth are attracted towards the energized stator poles rotation will occur

PERMANENT MAGNET

This type of motor is also known as “tin can” or “canstock” this type of motor is of low cost and low-resolution type motor this motor has permanent magnets added to the motor, and the rotor has no teeth as in VR motor but instead it is magnetized by alternating north and south poles which is situated in straight line parallel to the rotor shaft and with the help of this magnetized rotor poles the magnetic flux intensity increased and thus the permanent magnet motor has better torque characteristics when compared to the VR motor

HYBRID

This motor is expensive than the PM motor and the VR motor but it provides better performance in case of speed, step resolution, and torque, the hybrid stepper motors have the best features when compared other two the rotor is multi-toothed as in VR and has a concentric magnet around its shaft, the rotor teeth will be helpful to provide better path and it helps to guide the magnetic flux to the preferred locations and thus it will increase the torque characteristics

WHEN TO USE A STEPPER MOTOR

It can be used when the controlled movement is required this can also be used where we need to control the rotation angle, speed, position, and synchronism because of all these features the stepper motor has used for many applications such as printers, plotters, hard disc drives, medical equipment, automotive and fax machines

ADVANTAGES

  • Input pulse is proportional to the rotation angle of the motor
  • Motor has full torque at a standstill if the windings are energized
  • Good response to starting, stopping and reversing
  • It is very reliable due to the lack of contact brushes and the life of the motor depends upon the life of bearing
  • Response to digital input pulse provides open-loop control making it simple and less costly to control