seminar on ac – dc converters.pptx

7/27/2019 SEMINAR ON AC DC CONVERTERS.pptx

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SEMINAR ON AC

DC

CONVERTERS

BY:

ANKUR MAHAJAN

M.E. I&C REGULAR -2011

ROLL NO. 112505


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GOAL OF THE SEMINAR

SINGLE PHASE HALF WAVE & FULL WAVE

CONVERTERS.

SEMICONDUCTOR

DEVICES THE

HEART OF

INDUSTRIAL

ELECTRONICS


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MY OWN QUOTES :

THE DEVELOPMENT OF EVERY NATION DEPEND UPON

ITS POWER SOURCES, & POWER ELECTRONICS IS A

MAGIC WAND WHICH GENERATE POWER SOURCES

POWER ELECTRONICS IS A LIFE BLOOD FOR MODERN

COMPUTERS, COMMUNICATION & ELECTRONICSYSTEMS , THUS WITHOUT IT OUR LIFE COMES TO

HALT

WHAT IS THE MOST IMPORTANT REASON FOR RAPID

DEVELOPMENT IN THE FIELD OF POWER

ELECTRONIC DEVICES ?


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PIE CHART OF WORLS ENERGY

PRODUCTION LEVEL

FOSSIL FUELS

NUCLEAR

RENEWABLES

IN INDIA 70% OF ELECTRICAL ENERGY COMES FROM COAL

ACCORDING TO IEEE JOURNAL ON

POWER DELIVERY: WE HAVE NO

FOSSIL & NUCLEAR FUEL BY THE

END OF 22ND CENTURY.

87

%

6

%

7%

(A)USE EE

EFFICIENTLY.(B) IMPROVE

CONVERSION

EFFICIENCY.

(C) USE

RENEWABLES


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INTRODUCTION

WHAT IS RECTIFICATION ?

RECTIFICATION REFERS TO PROCESS OF

CONVERTING AN ALTERNATING VOLTAGE OR

CURRENT TO DIRECT VOLTAGE OR CURRENT.

RECTIFIERSRECTIFIER REFER TO POWER

ELECTRONIC CONVERTERS WHERE THE

ELECTRIC POWER FLOWS FROM A.C. SIDE TO

THE D.C. SIDE.

NOTE: IN MANY SITUATIONS THE SAME

CONVERTER CARRIES ELECTRICAL POWER

FROM D.C. SIDE TO A.C. SIDE - INVERTERS


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BECAUSE ON & OFF

STATE OF DIODE IS

DETERMINED BY THE

STATE OF THE

CIRCUIT.

BECAUSE THYRISTOR CAN BE TURNED

ON BY CONTROL TERMINAL. i.e. GATE


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ASSUMPTIONS :

ALL THE DEVICES & CIRCUIT COMPONENTS

ARE IDEAL i.e. Ton =Toff =zero

INPUT IS PURE SINE WAVE

CHARACTERISTICS OF AN IDEAL SWITCH


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TERMINOLOGIES

LET f BE THE INSTANTANEOUS VALUE OF ANY

VOLTAGE OR CURRENT ASSOCIATED WITH

RECTIFIER CIRCUIT, THEN


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TERMINOLOGIES (CONT.)

Angle at

Which SCR starts conducting

Angle at which SCR stops conducting


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SINGLEPHASEFULLYCONTROLLEDH/W

RECTIFIER


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FOR PURELY RESISTIVE LOAD

CURRENT FLOWS FROM TO THROUGH

LOAD BECAUSE SCR IS IN FPRWARD

CONDUCTION MODE.

-


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CALCULATIONS

Average value of output voltage

On solving

ttdvv iav sin22

1

cos12

iav

vv


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CALCULATION OF RMS VALUE OF

VOLTAGE

tdvvorms

2

2

1

tdtvv irms

22

sin22

1

tdtv

vi

rms

)2cos1(22

2

1

])2

2sin(

1[

2

tt

vv irms

)2cos1(2

12 ttSin


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CALCULATION OF RMS VALUE OF

VOLTAGE (CONT.)

On solving

Form factor

2

1

)2

2sin1(

2

irms

vv

cos1

)2

2sin1( 2

1

av

rms

vvformfactor

cos12

iavv

v


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RESISTIVEINDUCTIVE LOAD

to to


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RESISTIVEINDUCTIVE LOAD

Since thyristor does not conduct over the

entire input so it is called DISCONTINUOUSCONDUCTION MODE


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CALCULATIONS

t

tvtvvv imio sin2sin

otherwisev ,00

ttdvv iav sin22

1

)cos(cos2

,

iavv

vonsolving


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RMS VALUEOFOUTPUTVOLTAGE

2

122 )sin2

2

1( ttdvv irms

21

)2cos1(1

2

tdtv

v irms

21

2

2sin

2

2sin(

1

2

irms

vv

2

1

2

2sin2sin(

2

i

rms

vv

)2cos1(2

12 ttSin


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SINGLEPHASEHALFCONTROLLEDBRIDGE

Assume, load is highly inductive

Because 90% of loads are inductive

CASE I

T1

T4

D3

D2

LOADA

B


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At t =, D3 starts conducting and

-ve voltage appear across T1 & it starts

blocking voltage.

THIS PROCESS IS CALLED LINE COMMUTATION

T1

D2

A

B

to

SINCE LOAD IS HIGHLY INDUCTIVEFREEWHEELING CURRENT FLOWS

THROUGH D2-D3

FROM t = To +

D3

D2


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At t = , T4 is in forward blocking mode at t = +

T4 is triggered & +ve voltage appears across D2 and it

stops conducting.

At t = 2, D2 starts conducting and T4 is OFF, this is

called LINE COMMUTATION

D3

T4

A

B


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2+,

+

2

Since thyristor does not conduct over theentire input so it is called

DISCONTINUOUS CONDUCTION MODE

Avg. current rating of thyristor is < that of

diode, which is not desirable


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CALCULATIONS

cos1 mavv

V

Vav is +ve and Iav is also +ve so source is supplying power to the

load or we can say that load is PASSIVE.

Vav

------

1

0.5

/2

Vo

Io

Operation in 1st

Quadrant


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CASE II: CONTINUOUS CONDUCTION MODE

T1 T3

D4 D2

LOAD

DURING to

OPRATION OS SAME AS

THAT OF CASE I.

FROM to + D4

STARTS CONDUCTING & T3

IS IN FORWARD BLOKING

MODE. THUS NO

CONDUCTION.

T1 & D4 CONDUCTS.

A

B

-


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FROM to + FROM + to 2

T1

D4

At t = +, T3 IS

TRIGGERED & T1

COMMUTATES ( LINE

COMMUTATION)

T3

A

B

D4

FROM 2, D2 STARTS

CONDUCTING & T1 IS IN FORWARD

BLOKING MODE.

THUS NO CONDUCTION.

T3 & D2 CONDUCTS.


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2+,

2

+

Since thyristor conducts over the entire

input so it is called CONTINUOUS

CONDUCTION MODE


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CONTINUOUS

CONDUCTION MODE

DISCONTINUOUS

CONDUCTION MODE


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FULLY CONTROLLED BRIDGE

ASSUMPTIONS:

a) LOAD CURRENT IS

CONSTT. & RIPPLE FREE.

b) Io IS CONTINUOUS.IN THE +VE HALF, T1 T2

ARE FORWARD BIASED.

IN THE NEGATIVE HALF

T3 T4 ARE FORWARD

BIASED.

TI & T2 CONTINUE TO

CONDUCT TILL T3 & T4ARE TRIGGERED.


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FULLY CONTROLLED BRIDGE

SINCE THERE

ARE TWO PULSES

PER CYCLE SO IT IS

CALLED :TWO PULSE CONVERTER


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AVERAGE VALUE OF OUTPUT VOLTAGE

ttdvV mav

sin1

cos2 m

av

vV

onsolving

Thus, Vav is +ve from o /2Vav isve from /2

Vo

Io

-Vo


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REFERENCES

M.H.RASHID,POWER ELECTRONICS: CIRCUITS,

DEVICES & APPLICATIONS, PENTICE HALL OF

INDIA,(IIIRD Ed.),2004

CYRIL LANDER, POWER ELECTRONICS,

MCGRAW HILLS CO. ,(IIIRD Ed.), 1993

B.K. BOSE, MODERN POWER ELECTRONICS &

A.C. DRIVES, PEARSON EDUCATION INC.,2002


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seminar on ac – dc converters.pptx

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