VINYASH FINAL Report_project - Copy - Copy

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PROJECT REPORT

ON

Analysis of the Square Ring Micro-Strip Antenna forCircular Polarisation with Different Height of Di-electric

Substrate

Submitted in partial fulfillment for the award of degree

Of

BACHELOR OF TECHNOLOGY

ELECTRONICS AND COMMUNICATION ENGG.

SHOBHIT UNIVERSITY

Submitted by: Project guide:

Dhananjay Kr. Dubey (MRT09UGBEC019) Mr.Manoj Sharma

Sumit Kumar Singh (MRT09UGBEC074) Assistant Professor


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DECELERATION

We hereby declare that the project entitled Stimulation Of Soft Starting Of dc

Motor Using MATLAB submitted for the award ofB.Tech Degree in Electronics

And Instrumentation Engineering to SHOBHIT UNIVERSITY, the project has not

formed the basis for the award of any degree.

Date: Nov. 30, 2012.

Submitted by:

Name signature

VINYASH CHANDRA (MRT09UGBEI010)

ANKIT (MRT09UGBEI002)

GAURAV MISHRA (MRT09UGBEI004)


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CERTIFICATE

This is to certified that the project and entitled Stimulation Of Soft

Starting Of dc Motor Using MATLAB is the work carried out by the

members name students ofB.Tech, Shobhit University, MEERUT during

the year 2012 in partial fulfillment of the requirement for the award of

degree of Bachelor Of Technology (E&I Department).

(Mr.DEEPAK KUMAR) (Dr.D.V.RAI)

Internal Examiner HOD

E&I, Department

(Mrs.Shweta Choudhary)

Project Guide External Examiner


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ACKNOWLEDGEMENT

We owe a great many thanks to a great many people who helped and supported

me during this project.

We would like to express the deepest appreciation to Mrs. Shweta

Choudhary asst. prof. department of Electronics and Instrumentation

Engineering, Shobhit University; the guide of the project for guiding and

correcting various documents of ours with attention and care; who has the

substance of a genius; he continually and convincingly conveyed a spirit of

adventure to our project, and an excitement in regard to teaching. Without his

guidance and persistent help this project would not have been possible.

We express our thanks to the Head of Department, Dr. D.B.RAI, Electronics

and Instrumentation Engineering, Shobhit University, for extending his support.

We would also thank our Institution Shobhit University and our faculty

members without whom this project would have been a distant reality. We also

extend our thanks to ours family and well wishers.


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TABLE OF CONTENTS

ChapterNo. Title Page No.

1. Objective 7

2. Introduction 7

3. DC motor starter

Matlabsimulink model 8

4. DC motor 10

5. Motor model and problem

definition 11

6. Starting means of the motor 14

7. Thyristor 16

8. Full wave rectifier 17

9. Simulation of separately

excited DC motor 21

10. Switching circuit 23

11. Circuit breaker 25

12. Controlling circuit 2613. Scope 27

14. Conclusion 28

15. Bibliography 30


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1.Abbreviations and Symbols.

Ra Armature winding resistance

La Armature winding inductance

Rf Field winding resistance

Lf Field winding inductance

Kf Constant of proportionality between motor flux ( ) and field

current (if).

J Inertia of Motor

TL Applied mechanical/ Load Torque

ia Armature current

if Field current Motor speed (radian per sec)

rpm revolution per minute


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Stimulation Of Soft Starting

Of

DC Motor Using MATLAB.

1.Objective:-Starting of dc motor with the variation of the applied voltage gradually in equal

steps from zero to the rated value limiting the starting current and giving sufficient

time for the back emf, Eb to build up. This voltage variation is achieved byvarying the firing angle delay of the power electronic device (Thyristor, GTO,

IGBT, etc), used as building blocks of the converter circuit that feeds the line,

supplying the motor.

2.Introduction:-Starting of a motor is the most important aspect in the control and operation of amachine. It becomes the utmost responsibility of a control engineer to take care of

the starting of any motor so as to reduce the starting current that would rush into

the motor. Many techniques can be adopted for achieving effective and smooth

starting of a motor. This project highlights the soft starting of a dc machine.

Soft starting of a dc machine deals with the variation of the applied voltage

gradually in equal steps from zero to the rated value limiting the starting current

and giving sufficient time for the back emf, Eb to build up. This voltage variation

is achieved by varying the firing angle delay of the power electronic device

(Thyristor, GTO, IGBT, etc), used as building blocks of the converter circuit that

feeds the line, supplying the motor.


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For certain industrial applications, it becomes essential to run an electric machine

used to drive a job, at adjustable but constant speed. Such a requirement results in

an urge to control the speed of the drive in an accurate and efficient manner. One

of the best suited methods of speed control of a DC motor is the PWM (Pulse

Width Modulation) method of control. This is an efficient method of voltage

control method of speed. As the name indicates, this method uses pulse width

modulated voltage signals to achieve a smooth speed control technique.

3.DC Motor Starter, MatLab/Simulink Models.Three possible conventional means may usually be used to control or monitor the

level of the armature current when starting a dc motor. The three possible means

are:

1. Use of a gradually decreasing tapped resistance between the supply voltage and

the motor armature circuit.

2. Use of a chopper circuit between the supply voltage and the motor armature

circuit.

3. Use of a variable DC voltage source.The third mean seems to own certainly

superiority when compared to the two first means.

It is well known that when starting a dc motor and that is by connecting its

armature circuit directly to a DC voltage source, a high value of the armature

current is expected. Such high value is primarily due to the lack of the back

electromotive force (emf) of the motor. The back electromotive force is known to

be proportional to the motor speed. The high value of the armature current may


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cause troubles to the DC motor ( like reduction of its life time, creation of false

operation of the protective devices associated with the motor, etc).

One of the classical remedies to such problem is to insert a starting resistor in

series with the motor armature circuit. The starting resistor should be gradually

removed as the motor speeds up. A careful glance at such method is that even

though there will be a control or monitor of the level of the armature current, there

will be a waste of energy at each start-up maneuver.

To overcome the last disadvantage, power electronics circuitry can be introduced.

This is possible through the insertion of achopper circuit. The chopper circuit

should be controlled by a hysterisis controller. The duty of the hysterisis controller

is to monitor or keep the motor armature current between certain two pre-set

threshold values. Unfortunately, theinsertion of chopper circuit results in a new

drawback which consists of creating ripples in the armature current.

Another alternative of starting the DC motor is to use a variable DC voltage

source. The level of source voltage should be minimum at start-up and should

increase gradually as the motor speeds up. Increasing the level of the voltage

source should be done automatically. This alternative is realized through the use of

a controlled full wave rectifier (AC-DC converter). The position of firing angle of

the rectifier should be decided by a closed loop controller. The input to the

controller should be the motor speed. The job of the controller is to have a high

value of firing angle at start-up and decreasing it gradually as the motor speeds up.

The firing angle should reach and stick to zero value as the motor reaches steady

state conditions.


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A softstarter consists of only a few main components. These are the thyristors that

can regulate the voltage to the motor and the printed circuit board assembly

(PCBA) that is used to control the thyristors. In addition to this, there are the

heatsink and fans to dissipate the heat, current transformers to measure the current

and sometimes display and keypad and then the housing itself. It is more and

morecommon to offer integrated by-pass contacts in the main circuit minimizing

the power loss in normal operation.Depending on the model of the softstarter, it

can be equipped with a built-in electronic overload relay (EOL) eliminating the

need for an external relay, PTC input, fieldbus communication possibilities etc.


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4.DC motor:-A direct-current (DC) motor is a device for converting dc electrical energy into

rotating mechanical energy. All motors have several basic characteristics in

common. They include: A stator, which is the frame and other stationary

components (provides the fixed magnetic field, could be a permanent magnet or an

electromagnet); a rotor or armature, which is the rotating shaft and its associated

parts (many coils of wire are wound on a cylindrical shaft); auxiliary equipment,

such as a brush/commutator assembly for DC motors and a starting circuit for AC

motors.Possible operation modes

Description

The DC Machine block implements a separately excited DC machine.


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An access is provided to the field terminals (F+, F-) so that the machine model can

be used as a shunt-connected or a series-connected DC machine. The torque

applied to the shaft is provided at the Simulink input TL.

The armature circuit (A+, A-) consists of an inductor La and resistor Ra in series

with a counter-electromotive force (CEMF) E.

The CEMF is proportional to the machine speed.

KEis the voltage constant and is the machine speed.

In a separately excited DC machine model, the voltage constant KE is proportional

to the field current If:

whereLafis the field-armature mutual inductance.

The electromechanical torque developed by the DC machine is proportional to the

armature current Ia.

where KT is the torque constant. The sign convention for Teand TL is

The torque constant is equal to the voltage constant.


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The armature circuit is connected between the A+ and A- ports of the DC Machine

block. It is represented by a series Ra La branch in series with a Controlled

Voltage Source and a Current Measurement block.


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5.MOTOR MODEL AND PROBLEMDEFINITION:-

Figure shows a schematic diagram of a DC shunt motor connected to a DC voltage

supply. The field winding is usually represented by an inductance (Lf) in series

with the rotor resistance (Rf). Similarly, the armature is usually represented by a

back electromotive force (Ea) in series with the rotor winding resistance (Ra) and

the winding self inductance (La). As it is known from any design textbox in

electric machines like , field winding resistance (Rf) has usually a high value while

armature winding resistance (Ra) has a small value.


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The back electromotive force (Ea) is proportional to the flux ( ) created by the

stator winding and the motor speed ( ).Assuming, that there is a linear

relationship between and the flux ( ) and the field current (if), that is the

saturation effect is neglected, the dynamic model that can be used to represent the

shunt DC motor can be easily derived. It will be of the following form:

Operation called constant torque At constant excitation, the motors speed

depends on the voltage appliedto its armature. Speed can be varied from standstill


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to the rated voltage ofthe motor chosen according to the AC voltage supply.The

motor torque is proportional to the armature current, and the ratedtorque of the

machine can be obtained continuously at all speeds.

Operation called constant power

When a machine is powered with rated voltage, it is still possible to increase its

speed by reducing the excitation current. In this case the speed controller must

have a controlled rectifier bridge powering the excitation circuit. The armature

voltage therefore remains fixed and equal to the rated voltage and the excitation

current is adjusted to obtain the requisite speed.

Power is expressed as:

P = E . I with

E as its armature voltage, and

I the armature current.

The power, for a given armature current, is therefore constant in all speed ranges,

but the maximum speed is limited by two parameters:

- the mechanical limit linked to the armature and in particular the maximum

centrifugal force a collector can support,

- the switching possibilities of the machine are generally more restrictive. The

motor manufacturer must therefore be consulted to make a good choice of motor,

particularly with regard to speed range at a constant horsepower.

By connecting the motor terminals directly to full supply voltage, the expected

waveforms of the armature current , the field current, and the motor speed are

depicted in figure


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6.STARTING MEANS OF THE MOTOR:-Using Starting Resistance

One way of limiting the armature current level is to insert a starting resistance in

series with the armature circuit as shown in figure 3. The starting resistance should

gradually be removed as the motor speeds-up. The times of moving from one tap to

another tap are usually calculated from steady state analysis.The starting resistance


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was assumed to be of five parts. The parts were gradually short-circuited and that

is by pretending the existence of a circuit breaker poles across each part terminals.

Figure shows the Matlab/Simulink block of the starting resistance.


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Using Starting Chopper Circuit

Using Chopper circuit Mean. a) Circuit Topology b) Hysteresis Controller

Function

The second possibility of controlling the armature current is to use a step-up

converter. The step-up converter is usually attributed the name chopper in the

literature.


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Results when Using Chopper Circuit.a) Armature current b) Field current. c)

Motor speed


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As it can been seen, the chopper circuit did perform its duty as intended but that

was at the expense of delaying the motor from reaching its steady state (rated

value) in a short time. The motor reaches its rated speed at time = 8 seconds. The

ratio between the maximum and rated values of the armature current is 1.23 but the

armature current has a lot of ripples which might be harmful to the armature

circuitry.

Using Starting AC/DC Converter

An indirect way of controlling the armature current is to have a variable DCvoltage source. The level of the voltage source should be of minimum level at

start-up and should increase gradually as the motor back electromotive force builds

up. This is possible through the use of a controlled full wave rectifier similar to the

one shown in figure


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Using AC/DC Converter Mean.

At standstill the Back induced Emf in a DC motor is zero. Moreover, resistance of

the armature is as low as ~0.4ohm. Hence on direct application of line voltage very

high current rushes into the armature circuit. This may lead to damage the coil by

overheating. This makes it necessary to control the inrush current.

As the rotor starts running, back emf(Eb) gets induced and gradually builds up to

oppose the line voltage. Due to the building up of the back emf (Eb) in the armature

coil, the effective voltage at no load, is considerably reduced to 2-3V which

automatically limits the armature current. This limiting of armature current to

approximately 10% of the rated current helps to achieve safer and smoother

starting of a motor.

The role of a starter is to limit the armature current till the back emf (Eb) is built

up. Traditionally this has been achieved by adding resistance in series with the

armature at the starting stage and then gradually reducing it to zero. This resistance

reduces the initial current then as Ebgradually builds up; this resistance becomes

unnecessary and hence can be cut off from the circuit. This method can be either

manual or automatic but the heat dissipation across the resistance gives the alarm

about the need for sophisticated methods of starting.

For a more reliable and automated starting of a machine, the soft starting technique

is gaining importance now-a-days. The disadvantage of the previous method can

be over come in soft starting. Thus soft starting is more efficient than the resistance

method.


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7.Thyristor:-This is a controlled semiconductor made up of four alternating layers:P-N-P-N.

Itacts like a diode by transmission of an electric pulse on an electrode control

called gate. This closing (or ignition) is only possible if the anode has a more

positive voltage than the cathode. The thyristor locks itself when the current

crossing it cancels itself out. The ignition energy to supply on the gate is not

linked to the current to switch over. And it is not necessary to maintain a current in

the gate during thyristor conduction.

The thyristor has the main following characteristics:

in a closed state:

- avotage drop composed of a threshold voltage and an internal resistance,

- a maximum admissible permanent current (up to about 5000A RMS for the most

powerful components).

in an off-state:

- an invert and direct maximum admissible voltage, (able to exceed5000 V),- in general the direct and invert voltages are identical,

- an recovery time which is the minimum time a positive anode cathode voltage

cannot be applied to the component, otherwise it will spontaneouslyrestart itself

in the close state,

- a gate current to ignite the component.

There are some thyristors which are destined to operate at mains frequency, others

called fast, able to operate with a few kilohertz, and with an auxiliary extinction

circuit. Fast thyristors sometimes have dissymmetrical direct and invert locking

voltage. In the usual arrangements, they are often linked to a connected antiparallel

diode and the manufacturers of semiconductors use this feature to increase the


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direct voltage that the component can support in an off-state. Fast thyristor are now

completely superseded by the GTO, power transistors and especially by the IBGT

(Insulated Gate Bipolar Transistor).

8.Full wave rectifier:-Electronic speed controllers are supplied from a constant voltage from an AC

network and feed the motor with DC variable voltage. A diode or thyristor bridge,

usually single-phase, powers the excitation circuit. The power circuit is a rectifier.

Since the voltage has to be variable,the rectifier must be controllable, i.e. have

power components whoseconduction can be controlled (thyristors). The variation

of the output voltage is obtained by limiting more or less the conduction time of

thecomponents.


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The more the ignition of the thyristor is delayed compared to zero of the half cycle,

the more the average value of the voltage is reduced, reducing the motor speed

(remember that extinction of the thyristor steps in automatically when the current

passes by zero). For low power controllers, or controllers supplied by a storage

battery, the power circuit, sometimes made up of power transistors (chopper),

varies the continuous output voltage by adjusting the conduction time. This

operation mode is called PWM (Pulse Width Modulation).


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Output of the fullwave rectifier


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9.Simulation of separately exited dc motorFigure sows the circuit arrangement of soft starting of separately exited dc motor.

There is a switching circuit which converts the ac input into dc output and dc goes

to the dc machine. Field is exited by external voltage. Circuit breaker is used to

change the supply from ac link to dc link after reaching the rated speed. Here

comparator is used to give the signal to circuit breaker.

Soft starting of a dc machine deals with the variation of the applied voltage

gradually in equal steps from zero to the rated value limiting the starting current

and giving sufficient time for the back emf, Eb to build up. This voltage variation

is achieved by varying the firing angle delay of the power electronic device

(Thyristor, GTO, IGBT, etc), used as building blocks of the converter circuit that

feeds the line, supplying the motor.


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Here we can change the specification of dc machine by double click ondc machine

block.


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10. Switching circuit:-A Subsystem block represents a subsystem of the system that contains it. The

Subsystem block can represent a virtual subsystem or a nonvirtual subsystem. The

primary difference is that nonvirtual subsystems provide the ability to control when

the contents of the subsystem are evaluated. Nonvirtual subsystems are executed as

a single unit (atomic execution) by the Simulink engine. A subsystem is virtual

unless the block is conditionally executed and/or you have selected the block Treat

as atomic unit check box.You can create a subsystem in these ways:

Copy the Subsystem (or Atomic Subsystem) block from the Ports &Subsystems library into your model. You can then add blocks to the

subsystem by opening the Subsystem block and copying blocks into its

window.

Select the blocks and lines that are to make up the subsystem using abounding box, then choose Create Subsystem from the Edit menu.

Simulink software replaces the blocks with a Subsystem block. When youopen the block, the window displays the blocks you selected, adding Inport

and Outport blocks to reflect signals entering and leaving the subsystem.

Now we want to change the switching circuit then we double click on the swithing

circuit and we find the dialog box shown in figure


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Now we have to change the firing angle then we double click on the pulse

generater and find dioalogboxshown in figure

We put the value of firing angle and frequency in the given expression :-


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Phase delay(sec) = (*1/f)/360

Where in degree.

For the second pulse generater we use the following expression:-

Phase delay(seec) =1/2f+(*1/f)/360

The number of input ports drawn on the Subsystem block's icon corresponds to the

number of Inport blocks in the subsystem. Similarly, the number of output ports

drawn on the block corresponds to the number of Outport blocks in the subsystem.


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We put the value of firing angle and frequency in the given expression :-

Phase delay(sec) = (*1/f)/360

Where in degree.

For the second pulse generater we use the following expression:-

Phase delay(seec) =1/2f+(*1/f)/360

We match the minimum voltage to start the moter using firing angle, we fix thefiring angle in sec at which the starting voltage is found.

11. Circuit breaker :-The Breaker block implements a circuit breaker where the opening and closing

times can be controlled either from an external Simulink signal (external controlmode), or from an internal control timer (internal control mode).A series Rs-Cs

snubber circuit is included in the model. It can be connected to the circuit breaker.

If the Breaker block happens to be in series with an inductive circuit, an open

circuit or a current source, you must use a snubber.When the Breaker block is set

in external control mode, a Simulink input appears on the block icon. The control

signal connected to the Simulink input must be either 0 or 1 (0 to open the breaker,

1 to close it).

When the Breaker block is set in internal control mode, the switching times are

specified in the dialog box of the block.When the breaker is closed, it is


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represented by a resistance Ron. The Ron value can be set as small as necessary in

order to be negligible compared with external components (a typical value is 10

mohms). When the breaker is open, it has an infinite resistance. When we double

click on the circuit breaker then we find a dialogue box as shown in figure

12. Controlling circuitAfter reaching the rated speed of the moter we change the supply from ac to dc

using logic gate and circuit breaker. We fix a rated speed in constant block there

after we compare the running speed of the motor to the rated speed using

substractor. Output of the substractor goes to the comparator and give the output in


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form of 0 and 1. Output of the comparator is given to circuit breaker as input for

the breaker as shown in the figure below.

Circuit breaker 2 is on untill the decision is 1, when our rated speed is found then

decision becomes 0 and circuit breaker 3 is on which allows the dc supply to the

machine.We have to give the vallue in constant block. We double click on constant

and find the dialoge box as shown in figure.


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13. ScopeThe Scope block displays its input with respect to simulation time. The Scope

block can have multiple axes (one per port) and all axes have a common time range

with independent y-axes. The Scope block allows you to adjust the amount of time

and the range of input values displayed. You can move and resize the Scope

window and you can modify the Scope's parameter values during the

simulation.The Scope provides toolbar buttons that enable you to zoom in on

displayed data, display all the data input to the Scope, preserve axis settings from

one simulation to the next, limit data displayed, and save data to the workspace.


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The toolbar buttons are labeled in this figure, which shows the Scope window as it

appears when you open a Scope block.You can zoom in on data in both thex andy

directions at the same time, or in either direction separately. The zoom feature is

not active while the simulation is running.

To zoom in on data in both directions at the same time, make sure you select the

leftmost Zoom toolbar button. Then, define the zoom region using a bounding box.

When you release the mouse button, the Scope displays the data in that area. You

can also click a point in the area you want to zoom in on.

If the scope has multiple y-axes, and you zoom in on one set ofx-y axes, the x-

limits on all sets ofx-y axes are changed so that they match, because all x-y axes

must share the same time base (x-axis).


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14. ConclusionThree conventional means are usually used in the control of the level of the

armature current encountered at start-upconditions. These means are attributed in

this paper thenames:

- starting resistance mean,

- chopper circuit mean, and

AC-DC converter mean.

Development of Matlab/Simulink models for the previousmeans is the main

contribution of this paper. Based on thesimulation results of the developed models,

the last mean seems to:

- control the peak of the armature current to some extent

- have less ripples in the motor armature current

- avoid the waste of energy fact encountered usually in thecase of using starting

resistance.


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15. Bibliography :-1. M. S. Sarma, Electric Machines: Steady-state Theory and

DynamicPerformance, 2nd Edition, PWS publishing Company, Boston,

1996.

2. M. H. Rashid, Power Electronics: Circuits, Devices, andApplicationsPrentice Hall, New Jersey, 1988.

3.Matlab Software, Version 6.5, The Math Works, Inc., 2002.4. J. J. Cathey, ,Electric Machine: Analysis and Design Applying

MatlabMcGraw Hill Company, New York 2001.

5. P. C. Sen, Principles of Electric Machines and Power Electronics,JohnWiley & Sons Inc., New York, 1989

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VINYASH FINAL Report_project - Copy - Copy