seminar on ac – dc converters.pptx
TRANSCRIPT
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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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SINGLEPHASEHALFCONTROLLEDBRIDGE
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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SINGLEPHASEHALFCONTROLLEDBRIDGE
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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SINGLEPHASEHALFCONTROLLEDBRIDGE
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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SINGLEPHASEHALFCONTROLLEDBRIDGE
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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SINGLEPHASEHALFCONTROLLEDBRIDGE
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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SINGLEPHASEHALFCONTROLLEDBRIDGE
2+,
2
+
Since thyristor conducts over the entire
input so it is called CONTINUOUS
CONDUCTION MODE
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SINGLEPHASEHALFCONTROLLEDBRIDGE
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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