Stepper Motor

Introduction:
A Stepper Motor is a brush less, synchronous motor which divides a full rotation into a number of steps. Unlike a brush less DC motor which rotates continuously when a fixed DC voltage is applied to it, a step motor rotates in discrete step angles. 
The Stepper Motors therefore are manufactured with steps per revolution of 12, 24, 72, 144, 180, and 200, resulting in stepping angles of 30, 15, 5, 2.5, 2, and 1.8 degrees per step. The stepper motor can be controlled with or without feedback.

For more related information please refer:
Motor Types-Introduction
DC Motor
AC Motor
Special Types of Motor
Servo Motors


Working:
Stepper motors work on the principle of electromagnetism. There is a soft iron or magnetic rotor shaft surrounded by the electromagnetic stators.

The rotor and stator have poles which may be teethed or not depending upon the type of stepper. When the stators are energized the rotor moves to align itself along with the stator (in case of a permanent magnet type stepper) or moves to have a minimum gap with the stator (in case of a variable reluctance stepper). This way the stators are energized in a sequence to rotate the stepper motor.

Types:

1. Permanent Magnet Stepper
2. Variable Reluctance Stepper
3. Hybrid Stepper Motor

Stepping Modes:

There are three stepping modes of a stepper motor. The stepping mode refers to the pattern of sequence in which stator coils are energized.

1. Wave drive (One phase ON at a time):In wave drive stepping mode only one phase is energized at a time.


2. Full drive (Two phase ON at a time):In full drive, two phases are energized at a time.


3. Half drive (One and two phase ON at a time):In half drive, alternately one and two phases are energized. This increases the resolution of the motor.

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