Presentation 6
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Transcript of Presentation 6
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DC DCCONVERTER(DC CHOPPER(DC CHOPPER
ASNILELEKTRO FT UNPELEKTROFTUNP
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BLOCK DIAGRAM OF DC DC CONVERTERSBLOCKDIAGRAMOFDCDC CONVERTERS
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Achopperisastaticdevicewhichisusedtoobtainavariabledcvoltagefromaconstantdcvoltagesource.Achopperisalsoknownasdctodcconverter.Thethyristor converteroffersgreaterefficiency,fasterresponse lower maintenance smaller size and smoothresponse,lowermaintenance,smallersizeandsmoothcontrol.Choppersarewidelyusedintrolleycars,battery operated vehicles, traction motor control,batteryoperatedvehicles,tractionmotorcontrol,controloflargenumberofdcmotors,etc..Theyarealsousedinregenerativebrakingofdcmotorstoreturnenergybacktosupplyandalsoasdcvoltageregulators.
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Choppersareoftwotypes:Stepdownchoppersp ppStepupchoppers
In stepdown choppers, the output voltage will be less than thep pp , p ginput voltage whereas in stepup choppers output voltage will bemore than the input voltage.
PRINCIPLEOFSTEPDOWNCHOPPERChopper
i0
pp
+
V V0R
Fig.2.1:StepdownChopperwithResistiveLoad
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Figure 2.1 shows a stepdown chopper with resistive load.The thyristor in the circuit acts as a switch. When thyristor is ON,supply voltage appears across the load and when thyristor is OFF,the voltage across the load will be zero. The output voltage andcurrent waveforms are as shown in figure 2.2.g
v0V
Vdc
ttON tOFF
V/R
i0
Idct
T
Fig. 2.2: Step-down choppers output voltage and current waveforms
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STEPDOWNCHOPPERWITHRLLOAD
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CLASSIFICATION OF CHOPPERSChoppersareclassifiedasfollowspp ClassAChopper ClassBChopper Class C Chopper ClassCChopper ClassDChopper ClassEChopper
CLASS A CHOPPER
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CLASS B CHOPPER
Fig.2.16:ClassBChopper
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CLASS C CHOPPER
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CLASS D CHOPPER
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CLASS E CHOPPER
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Exercise
A Chopper circuit is operating on TRC at a
Exercise
A Chopper circuit is operating on TRC at afrequency of 2 kHz on a 460 V supply. If the loadvoltage is 350 volts calculate the conductionvoltage is 350 volts, calculate the conductionperiod of the thyristor in each cycle.