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[1]

STEPPER MOTOR

Under the Guidance of

[guide teacher name]

By

Dishant Kumar (2K8/EE/824)

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[2]

INTRODUCTION TO STEPPER MOTOR

Electromechanical device which converts electrical

pulses into discrete mechanical movements

Shaft of a stepper motor rotates in discrete step

increments when electrical pulses are applied

Sequence of the applied pulses is directly related to

the direction of motor shafts rotation.

Speed of rotation is directly related to thefrequency of input pulses applied

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[3]

STEPPER MOTOR THEORY OF OPERATION

PM type stepper motor

permanent magnet is

rotor and coils are put

on stator. The rotor will move

precisely 90 degrees for

each pulse of electricity

that the motor receives

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CLOCKWISE & COUNTERCLOCKWISE CONTROL

CounterClockwise Rotation

ControlSequence

ControlSequence

Clockwise Rotation

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THEORY

When current flows holding torque is produced

Without power, rotor will detent oralign to magnetic

poles ,here 4 Such positions are present.

changing the current flow to the next stator winding,

the magnetic field will be changed 90& rotor will

move 90 before its magnetic fields will again align

with the change in the stator field.

The turn of the motor is controlled by the electric

current which pours into different stator terminals

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STEPPER MOTOR TYPES

There are three basic stepper motor

types.

Variable-reluctance

Permanent-magnet

Hybrid

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VARIABLE-RELUCTANCE TYPE

Consists of a soft ironmulti-toothed rotor and awound stator.

When the stator windingsare energized with DCcurrent &the poles becomemagnetized

Rotation occurs when therotor teeth are attracted tothe energized stator poles.

Crossectional view

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PERMANENT MAGNET (PM) TYPE

Rotor of PM typeCrossectional view

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HYBRID TYPE

Step Angles For HbStepper Motor RangeFrom 3.6to 0.9 DegreeWith100 400 Steps PerRevolution

Detent, holding anddynamic torquecharacteristics of themotor are bettercompared to both the VRand PM types. Crossectional View

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APPLICATION

Used in controlledrotation angle, speed,

position applications.

Printers, Plotters, HighEnd Office Equipment,Hard Disk Drives,Medical Equipment,

Fax Machines,Robotics, automotiveAnd Many More. Paper drive mechanism

Using stepper machine

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SOME PRACTICAL FIGURES

Used in CD-ROMDriveUsed in Dot Matrix Printer

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STEPPING MODES

Full Step Drive ----200 full steps per

revolution and 1.8 full step angle

Half Step----- 400 full steps per revolution

and 0.9 full step angle

Microstepping (Continiously varying motor

currents )----more than 50000 full steps per

revolution and (1/256) full step angle

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TORQUE VS ROTOR ANGLE & SPEED

CHARCTERISTICS

Graph between Torque

and speed

Torque vs. Rotor angle

graph

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SINGLE STEP RESPONSE

The curve shows behavior of

rotor with one step pulse

step time dependent on the

ratio of torque to inertia &

the type of driver used

Acceleration causes

overshoots & ringing as

shown

This behavior is reduced by

microsteppingPositional Accuracy Of

A Stepper Motor

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STEP ANGLE ACCURACY

Stepper motor is popular

due to its accuracy and

repeatability

Step angle accuracy is 3-5% of one step

Positional Error

Step Position Error

Positional accuracy

of a stepper motor

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ADVANTAGES OF STEPPER MOTORS

The rotation angle of the motor is proportional to the inputpulse

Excellent response to starting, stopping/reversing

The motors response to digital input pulses provides open-loop

control It is possible to achieve very low speed synchronous rotation

A wide range of rotational speeds can be realized

Very reliable since there are no contact brushes in the motor

Accuracy of 3 5% of a step and this error is non cumulativefrom one step to the next

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CONCLUSION

All types and characteristics of a stepper motor

are studied throughout this paper.

These are very popular in our day to day life

due to a lot of advantages and also in digital

control circuits, such as robotics because they

are ideally suited for receiving digital pulses

for step control

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THANK YOU