A SEMINAR

on

STEPPER MOTORSSubmitted in partial fulfillment of the requirements for the award of the degree in

BACHELOR OF TECHNOLOGY

IN

ELECTRICAL AND ELECTRONICS ENGINEERING

By

V.SUMANTH(12BF5A0212)

Under the esteemed guidance of

Mr.B.HEMANTH KUMAR M.Tech,

Assistant Professor

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERINGSRI VENKATESWARA COLLEGE OF ENGINEERINGKarakambadi road, Tirupati-517507, A.P

(Affiliated to J.N.T.U, Anantapur)(2012 – 2015)

CONTENT: INTRODUCTION

PRINCIPLE OF STEPPER MOTOR

TYPES OF STEPPER MOTOR

STEPPER MOTOR PARAMETERS

STEPPING MODES

MECHANICAL PARAMETERS, LOAD, FRICTION, INERTIA

CHARACTERISTICS

SINGLE STEP RESPONSE AND RESONANCES

ADVANTAGES

DISADVANTAGES

APPLICATIONS

CONCLUSION

INTRODUCTION:

An electric motor is a machine that converts electrical energy into

mechanical energy for obtaining useful work.

A stepper motor is a brushless DC motor whose rotor rotates in a discrete

angular increments when its stator is energised in a programmed manner

The first stepper motor is invented by walker i.e., salient pole variable

reluctance stepper motor.

As far as application of stepper motors are concerned McCelland

described application of the stepper motor in British warships.

The modern stepper motor was first described by Thomas and Fleischauer in

1957

The permanent magnet hybrid stepper motor was invented by Feirtag and

Donahoo of General Electric Co. (GEC) in 1952.

PRINCIPLE OF STEPPER MOTOR

A stepper motor is an electromechanical device which converts electrical

pulses into discrete mechanical movements.

The shaft or spindle of a stepper motor rotates in discrete step increments

when electrical command pulses are applied to it in the proper sequence.

The motors rotation has several direct relationships to these applied input

pulses.

The sequence of the applied pulses is directly related to the direction of

motor shafts rotation.

The speed of the motor shafts rotation is directly to the frequency of the

input pulses.

TYPES OF STEPPER MOTOR:

As far as construction is concerned, stepper motors may be divided into two major groups.

Without permanent magnet and with permanent magnet

WITHOUT PERMANENT MAGNET

Variable reluctance stepper motor

WITH PERMANENT MAGNET

CLAW POLE

HYBRID

ENHANCED HYBRID

DISC MAGNET

VARIABLE RELUCTANCE STEPPER MOTOR

CLAW POLE STEPPER MOTOR

HYBRID STEPPER MOTOR

DISC MAGNET STEPPER MOTOR

STEPPER MOTOR PARAMETERS

STEP ANGLE is defined as the angular displacement of the rotor in response

to each pulse

CRITICAL TORQUE is representing the maximum load torque at which the

rotor doesn’t move when an exciting winding is energized

LIMITING TORQUE is defined for a given pulsing rate or stepping rate

measured in pulses per second, as the maximum load torque at which the

motor follows the control pulses without missing any step

SYNCHRONOUS STEPPING RATE is defined as the maximum rate at which

the motor can step without missing steps.

SLEWING RATE is defined as the maximum rate at which the motor can step

unidirectionally.

STEPPING MODES

Full step operation

2 phase ON operation

Half step operation

Micro stepping operation

MECHANICAL PARAMETERS, LOAD,

FRICTION, INERTIA

The performance of a stepper motor system ( driver and motor) I s also highly dependent on the mechanical parameters of the load.

The load is defined as what the motor drives. it is typically frictional, inertial or a combination of the two

A minimum torque level is required throughout the step in over to overcome this friction

Increasing a frictional load lowers the increases the positional error. The converse is true if the frictional load is lowered.

Inertia is the resistance to changes in speed. A high inertial load requires same would apply for braking.

The rotor oscillations of a stepper motor will vary with the amount of friction and inertia load.

CHARACTERISTICS

Static and dynamic are the two characteristics which are classified in

stepper motor.

Static characteristics is again classified into two types. Namely, torque-

angle curve and torque current curve.

DYNAMIC CHARACTERISTICS

SINGLE STEP RESPONSE AND RESONANCE

When one step pulse is applied to a stepper motor the rotor behaves in a

manner as defined by the below curve.

The step time ‘t’ is the time it takes the motor shaft to rotate one step angle

once the first step pulse is applied.

Step time is highly dependent on the ratio of torque to inertia (load) as well

as the type of driver used.

Since the torque is a function of the displacement it follows that the

acceleration will be.

The settling time T is the time it takes these osccillations or ringing to cease.

ADVANTAGES

Excellent response to starting/stopping/reversing.

Very reliable since there are no contact brushes in the motor.

Less costly to control.

It is possible to achieve very low speed synchronous rotation with a load

that is directly coupled to the shaft.

Precise positioning and repeatability of movement since good stepper

motors have an accuracy of 3-5 % of a step and this error is non cumulative

from one step to the next.

DISADVANTAGES

Resonance can occur if not properly controlled.

Not easy to operate at extremely

APPLICATIONS

Stepper motors are used in a wide variety of applications in industry, including computer peripherals, business machines, motion control, and robotics, which are included in process control and machine tool applications. A complete list of applications is shown below

COMPUTER PERIPHERALS- floppy disc, printer, tape reader, plotter etc.,

BUSSINESS MACHINES- copy reader, copy machine, banking systems, type writer, card sorter.

PROCESS CONTROL- carburettor adjusting, valve control, conveyor, in process gaging, assembly lines, silicon processing, ic bonding, laser trimming, liquid gasket dispensing, mail handling systems.

MACHINE TOOLS- Milling Machines, Drilling Machines, Grinding Machines,Electron Beam Welder, Laser Cutting, Lathes, Sewing.

CONCLUSION

THANK YOU

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