Stepper motor

• Definition: A stepper motor is a special type of electric motor that moves in increments, or steps.
• A stepper motor or step motor or stepping motor is a brushless DC electric motor that divides a full rotation into a number of equal steps.
• The stepper motor is known by its property to convert a train/series of input pulses (typically square wave pulses) into a precisely defined increment in the shaft position.

• Each pulse moves the shaft through a fixed angle.

• DC voltage is applied as an excitation to the coils of windings and each winding terminal is connected to the source through a solid state switch.

• Depends on the type of stepper motor, its rotor design is constructed such as soft steel rotor with salient poles, cylindrical permanent magnet rotor and permanent magnet with soft steel teeth.

Types of Stepper Motors

There are three basic categories of stepper motors (depend on rotor arrangement), namely

1) Permanent Magnet Stepper Motor

2) Variable Reluctance Stepper Motor

3) Hybrid Stepper Motor

Permanent Magnet Stepper Motor

• The permanent magnet design motor is perhaps the most common among several types of stepper motors.
• As the name implies, it adds permanent magnets to the motor construction.
• This type of stepper motors is also referred as can- stack motor or tin-can motor.
• The main advantage of this motor is its low manufacturing cost.
• This type of motor has 48-24 steps per revolution.

Variable Reluctance Stepper Motor:

• It is the basic type of stepper motor that has been in existence for a long time and it ensures easiest way to understand principle of operation from a structural point of view.

• As the name suggests, the angular position of the rotor depends on the reluctance of the magnetic circuit formed between the stator poles (teeth) and rotor teeth.

• Step angle (a) : Step angle is defined as the angle which the rotor of a stepper motor moves when one pulse is applied to the input of the stator.

• step angle is expressed in degrees.

• The resolution (accuracy) positioning the stepper motor is

• The resolution of decided by step angle