Stepper motors - Working and applications


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A stepper motor is an electromagnetic device which converts electrical pulses into rotational motion. These motors rotates in discrete angular steps in response to programmed sequence of input electrical pulses.

Working of stepper motor:

Stepper motors rotate a fixed angle with each input pulse. The rotor is normally a fixed magnet with several poles and a stator with several windings. A single magnet rotor and a four-section stator, which gives a 90° rotation for each input phase.

Stepper motors are the only motor that is digital, in that they step one position for each input pulse. Changing the sequence of the driving phases can reverse the stepper motors. Stepper motors are
available with stepping angles of 0.9°, 1.8°, 3.6°, 7.5°, 15°, and 18°, up to 90°.

Because the motor steps by a fixed angle, a known angle with each input pulse feedback is not required. However, since only the relative position is known, loss of power can cause loss of position information, so that in a system using stepper motors, a position reference is usually required.

Applications of stepper motor:

  • Used in positioning systems

  • They are used in numeric control of machine tools.

  • The Stepper Motor are in spacecrafts launched for scientific explorations of the planets etc.

  • The stepper motor also use in X-Y plotter and robotics.

Advantages:

  • Excellent response to starting/stopping/reversing

  • It is possible to achieve very low speed synchronous rotation with a load that is directly coupled to shaft

  • The motors response to digital input pulses provides open loop control, making the motor simpler and less costly to control.

Disadvantages:

  • Resonance can occur if not properly controlled

  • Not easy to operate at extremely high speeds.


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