Stepper Motor Working, Types, Applications

ICE 3015: CONTROL SYSTEM
COMPONENTS
Class 12: Stepper Motors – Types and
Working
Dr. S. Meenatchisundaram
Email: meenasundar@gmail.com
Control System Components (ICE 3015)
Dr. S.Meenatchisundaram, MIT, Manipal, Aug – Nov 2018

Types of Windings:
• The step motors are mostly two phase motors.
• unipolar
• Bipolar
Unipolar:
• In unipolar step motor there are two winding per phase. The two
winding to a pole may have one lead common i.e. centre tapped.
• The unipolar motor so, have five, six or eight leads.
• In the designs where the common of two poles are separate but
centre tapped, motor have six leads.
• If the centre taps of the two poles are internally short, the motor has
five leads.

Unipolar:
• Eight lead unipolar facilitates both series and parallel connection
whereas five lead and six lead motors have series connection of
stator coils.
• The unipolar motor simplifies the operation because in operating
them there is no need to reverse the current in the driving circuit.
These are also called bifilar motors.

Bipolar:
• In bipolar stepper there is single winding per pole.
• The direction of current need to be changed by the driving circuit so
the driving circuit of the bipolar stepper becomes complex.
• These are also called unifilar motors.

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)
2. Full drive (Two phase ON at a time)
3. Half drive (One and two phase ON at a time)

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 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

Wave drive:

Full drive:

Half drive:

Structure:

Internal Structure:

Internal Structure:
• The rotor is made up of a permanent
magnets core with two soft iron discs
with teeth on the periphery.
• The number of teeth decides the step
angle of the motor.
• The teeth on the front disk form the
permanent magnetic south poles
whereas the teeth on the rear disk form
the permanent magnet north poles.
• The alignment of the teeth is done in
such a manner that the teeth on one
disc are positioned between the space
in the two consecutive teeth on the
other disc and vice versa.

Internal Structure:
• PCB has five output wires – four wires each connected with two
alternate coils and one for common wire.

Introduction:
• A Stepper Motor or a step motor is a brushless, synchronous motor
which divides a full rotation into a number of steps.
• Unlike a brushless 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.
• In the example below you may notice that there are 4 distinct steps
for the rotor to make a complete 360 degree rotation.
• This defines the step angle at 90 degrees.

Introduction:
• Since this motor does move in a discreet fashion, we can say that a
stepper motor is actually a digital motor.
• This characteristic makes it very suitable for digital interfaces such
as with a microcontroller.

Why a Stepper Motor?
• Relatively inexpensive
• Ideal for open loop positioning control
− Can be implemented without feedback
− Minimizes sensing devices
− Just count the steps!
• Torque
− Holds its position firmly when not turning
− Eliminates mechanical brakes
− Produces better torque than DC motors at lower speeds
• Positioning applications

Components:
• Consists of
− Stators
− Holds multiple windings/phases
− A Rotor
− Magnetized
− Non-magnetized
Stator:
• As the name implies this is a stationary component.
• Each stator will be wrapped with multiple windings or phases that
will be energized using a voltage source, initiating current flow
through the winding to produce a polarity on each end or pole of the
stator.

Components:

Components:
• Voltage applied to winding initiates current flow
• Magnetic flux begins to flow

Stepper Motor Working, Types, Applications

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