stepper motor(encrypted)
DESCRIPTION
We know that electric motor is a machine that converts electrical energy into mechanical energy. But there difference between conventional motor and stepper motor. 1. Input to stepper motor is in the form of electric pulses whereas input to conventional motor is from constant voltage source 2. A CM has a free running shaft whereas shaft of SM moves through angular steps. So this presentation will help to understand the basic operating principal of stepper motor, its types and some applicationsTRANSCRIPT
STEPPER MOTOR
By,
Rohini Haridas
Assistant Professor,
Dept of Electrical Engineering,
SSGM College of Engineering,Shegaon
Introduction
�A stepper motor is a form of ac motor. The input given to
this motor is in the form of electric pulses.
�Stepper motor is known by its important property to convert
a train of input pulses i.e. square wave pulse into a precisely
defined increment in the shaft position.
�Each pulse moves the shaft through a fixed angle.
�The angle through which the motor turns or shaft moves for
each pulse is known as the step angle, expressed in degrees
�As such angle is dependent on the number of input
pulses,the motor is suitable for controlling position by
controlling the number of input pulses
Step Angle
�The magnitude of step angle for stepper motor is given by
Where,
α = Step angleα = Step angle
ms = number of stator phases
Nr= Number of rotor poles or teeth
Steps per revolution is given by i.e. resolution
α
0360=
Numerical
1. Calculate the stepping angle for a three phase ,24 pole
permanent magnet stepper motor
Given:
ms = 3
Nr = 24Nr = 24
Solution :
= 360/(3*24)
=step/50
Numerical
2. Calculate the stepping angle for a three phase ,16-teeth
variable reluctance stepper motor
Given:
ms = 3
Nr = 16Nr = 16
Solution :
= 360/(3*16)
=step/5.7 0
Difference between Conventional
Motor and Stepper motor
� Input to SM is in the form of electric pulses whereas input
to CM is from constant voltage source
�A CM has a free running shaft whereas shaft of SM moves
through angular steps
Types of stepper motors
�Permanent Magnet Stepper Motor
�Variable Reluctance Stepper Motor
Rotor
Stator
Coils
Outside Casing
StatorCoils
2
1
S
N
1
2
Stator
Rotor
Internal components of a Stepper Motor
Permanent Magnet Stepper Motor
Permanent Magnet Stepper Motor
Rotor will always orient so that the nearest rotor south pole is aligned with the energized stator poles
Rotor will always orient so that the nearest rotor south pole is aligned with the energized stator poles
1
N
SStators
Cross Section of a Stepper Motor
2 2
S
1N
Rotor
Four Steps per revolution i.e. 90 deg. steps.
Eight steps per. revolution i.e. 45 deg. steps.
Variable Reluctance Stepper Motor
�The principle of operation of a variable reluctance
stepper motor is based on the property of flux lines to
occupy low reluctance path.
� The stator and rotor therefore get aligned such that
the magnetic reluctance is minimum
Variable Reluctance Stepper Motor
Practical Stepper motor operation
The top electromagnet (1) is turned on, attracting the nearest teeth of a gear-shaped iron rotor. With the teeth aligned to electromagnet 1, they will be slightly offset from electromagnet 2
The top electromagnet (1) is turned off, and the right electromagnet (2) is energized, pulling the nearest teeth slightly to the right. This results in a rotation of 3.6°in this example.
The bottom electromagnet (3) is energized; another 3.6°rotation occurs.
The left electromagnet (4) is enabled, rotating again by 3.6°. When the top electromagnet (1) is again enabled, the teeth in the sprocket will have rotated by one tooth position; since there are 25 teeth, it will take 100 steps to make a full rotation in this example.
APPLICATIONS
Film Advance
Labeling Machines
Rotating Tube Cutter
Advantages:-
Low cost for control achieved
Simplicity of construction
Low maintenance
Advantages
Will work in any environment
+
Control sequence to turn a stepper motor
Step 1 0 0 1 1
Step 2 1 0 1 0
Step 3 1 1 0 0
Step 4 0 1 0 1
CW CCW