Step Motors

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A stepper motor (sometimes called a step motor or stepping motor) is a DC motor with a fixed number of steps that make a full rotation.  The motor can be commanded to move to any one of those step locations and hold position without any need for a position sensor – assuming it is properly sized with regard to the torque and speed requirements of the application.  This is known as “open loop” control.

Stepper motors are controlled by alternately energizing the winding in the motor.  Stepper drives are used to control the high-power DC pulses to the motor, and thusly to control the motion of the motor’s shaft with great precision.

Two-phase stepper motors can be uni-polar or bipolar.  While uni-polar motors are popular with hobbyists, most industrial stepper motors are bi-polar.  Bi-polar motors are more efficient and powerful for a given weight.
A Stepper Motor or a step 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.


How a stepper motor works?

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. Get more information about working of stepper motors through interesting images at the stepper motor Insight.


A-NDC 94, 96_5x5-min