Stepper motor

Stepper motors are those where positioning the rotary movement is carried out in finite steps. Thus continuous rotation of AC or Dc motors is inhibited here. Since stepper motors operate under open loop control, they are inexpensive. A mechanical pulse rotation is developed for every electrical pulse in stepper motors. The major components of a stepper motor are permanent magnet, yoke, rotor and stator coils. The stator has a winding made of concentrated coils on distinct poles. A permanent magnet cylinder is fixed to the rotor.  The insertion of stator windings on outside edge of the yoke has to be done with extra care.  The rotor shaft is located at the centre of the yoke, mounted on the bearings. There are two poles with single winding system in a single phase stepper motor.  The smallest angle that the rotor can rotate under single pulse is known as step angle. The peak torque applied is known as holding torque before rotation of rotor and the torque required to reach synchronous mode is termed as pull in torque.