Upload
dangtu
View
229
Download
0
Embed Size (px)
Citation preview
EG1108ElectricalEngineering~AdditionalProblemsforPart2
1
1. Therectifiersupplyshowninthefigurebelowisusedaspartofanelectronicdevice.The
inputisanACvoltagesourcewithafrequencyof50Hzandapeakamplitudeof200V.The
transformerprimarytosecondaryratio=2:1.Theloadresistanceis100Ω.
(a) Determine the output DC voltage. What is the peak‐to‐peak ripple in the output
voltage?Whatisthepercentageripple?
(b) Sketchwaveformsforvsandvo,respectively.
(c) Suggestanadditionalcomponenttobeaddedtotheabovecircuit,whichcanyielda
smoothertheoutputvoltage.Drawtherevisedcircuit.
2. Considerthetransformercircuitshowninthefigurebelow.Thetransformerturnsratiois
1:2.Theinputtothecircuitisthevoltagesource,vs(t).Determinetheoutputvoltage,vo(t),
acrossthe2Hinductor.
3. ADCpowersupplyconsistsofatransformerfeedingahalf‐waverectifiertogetherwitha
capacitorfilter.ItsuppliesaDCcurrentof1Aat20VDCtoanelectronicequipment.The
ACinputsourceis230V(rms)at50Hz.Thefiltercapacitorhasacapacitanceof60,000μF.
a) Drawthecircuitdiagramofthesupplyarrangement.
b) Determineasuitablewindingratioforthetransformer.
c) Determinethemagnitudeofthepeak‐to‐peakrippleintheoutputvoltage.
2
EG1108ElectricalEngineering~AdditionalProblemsforPart2
2
4. Showninthefigurebelowaretheexpressionsoftheprimaryandsecondaryvoltagesofan
ideal transformer. Assume that the transformer reluctance 25 , the numbers of the
turnsoftheprimaryandsecondarywindingsare1 210, 5N N ,respectively.
(a) Giventhewaveformsofi1(t)andi2(t)asthefigurebelow,
sketchthewaveformsoftheinducedvoltages,v1(t)andv2(t).
5. Asoundsystemwithaloudspeakercanberepresentedinacircuitdiagrambelow.Assume
thattheinternalresistanceofthesourceis0.5,andtheresistanceoftheloadis8.
Mi1(t) i2 (t)
2
Ldd ti1(t)
v2(t) 2Mdd ti2(t)
Ldd ti1(t)
v1(t) 1 M dd ti2(t) L1 L2
L1N1 ,
2
L2N2 , M 2 L1 L2 for no flux leakage and perfect coupling
i1(t)
i2(t)
1A
1A
EG1108ElectricalEngineering~AdditionalProblemsforPart2
3
(a) Findanappropriatetransformerturnsratio,whichresultsinimpedancematching.
(b) Given ( ) 230 2 cos( )sv t t Vandwiththetransformerturningratioobtained in
(a),findtheaveragepowersconsumedbytheloadandbytheinternalresistor.
(c) Given ( ) 230sv t V and againwith the transformer turning ratio obtained in (a),
findtheactualpowersconsumedbytheloadandbytheinternalresistor.
(d) Forboth(b)and(c),determinethepowerconsumedbythetransformer.
6. SuggestaDCpowersupplycircuitthatcanbeusedtostepdowntheelectricsourcefrom
themains(230VAC)topowerupyourlaptop,whichtakes5VDC.Drawthecircuitwith
necessarycomponents.Willyouuseyourdesignforyourownlaptop?Whyorwhynot?
7. ForACenvironments,showthattheprimaryandsecondaryvoltages inthephasor form
aregivenasthoseinthefigurebelow.
Hint:Assume 1 1 1( ) 2 cosi t r t and 2 2 2( ) 2 cosi t r t .
8. ThetransformerisconnectedtoaloadinductorwithinductanceL=2H,asshowninthe
figurebelow.Recallthatthetransformerreluctance 25 , thenumbersoftheturnsof
theprimaryandsecondarywindingsare1 210, 5N N ,respectively.Determinetheratio
oftheprimaryandsecondarycurrents(inphasor).
Whyistheusualtransformerpropertybelownolongervalidinsuchasituation?
1 2
2 1
I N
I N
I1
M
L1 L2
I2
1V L1j I1 j I2M 2V L2j I1 j I2M
EG1108ElectricalEngineering~AdditionalProblemsforPart2
4
9 Showninthefigurebelowaretheexpressionsoftheprimaryandsecondaryvoltagesofan
idealtransformerinthephasorforminACenvironments.
Theprimaryandsecondaryinductancesofthetransformerarerespectivelygivenby
2 21 2
1 2 1 2, ,N N
L L M L L
where is the reluctance of the transformer. Let1,peakV and
2,peakV are respectively the
peakvaluesoftheprimaryandsecondaryvoltagesofthetransformer.Showthat
2,peak 2
1,peak 1
V N
V N
10. Thefollowingtransmissionsystemisusedtotransmitelectricpowerfromthesourceto
anACdevice.
Determine the average power lost on the transmission line and the average power
consumedbytheload.Whatisthepowerefficiency?
11. FindI1andI2inthecircuitbelow.
I1
M
L1 L2
I2
1V L1j I1 j I2M 2V L2j I1 j I2M
EG1108ElectricalEngineering~AdditionalProblemsforPart2
5
12. Findallvoltagesandcurrentsinthecircuitbelow.
13. FindV0inthecircuitbelow.
14. FindV0inthecircuitbelow.
15. Theoutputstageofanamplifieristobematchedtotheimpedanceofaspeakerasshowin
thefigurebelow.Iftheimpedanceofthespeakeris8andtheamplifierrequiresaload
impedanceof3.2k,determinetheturnsratiooftheidealtransformer.
16. Thewaveformshownbelowisappliedasaninputtothehalf‐waverectifiercircuitbelow.
(a)Plottheoutputwaveform,vo(t).(b)Whatisthedcvoltageoutput?
EG1108ElectricalEngineering~AdditionalProblemsforPart2
6
17. Shownbelow is a half‐wave rectifier circuitwith a filter. Plot the outputwaveformand
estimatethepeak‐to‐peakrippleforC=150F.
18. Anelectroniccalculatoroperatesonadcsupplyof6V.Thissupplyisobtainedfromahalf‐
waverectifierwitha filter. If thecalculatorcanbemodeledasa10k resistanceandit
cantolerateamaximumpeak‐to‐peakvariationof0.1Varoundthedcvalue,calculatethe
minimumvalueofcapacitorthatcanbeusedinthefilter.Assumeacinputis50Hz.
19. Shownbelowisafour‐diodefull‐waverectifiercircuit.(a)Plottheoutputvoltagevo(t).(b)
Determinethemaximumreversevoltageonanydiode.(c)Whatisthedcoutputvoltage?
20. Shownbelowisatwo‐diodefull‐waverectifiercircuit.Plottheoutputvoltagewaveform,
andestimatethepeak‐to‐peakripple.Determinethemaximumreversevoltageoneither
diode.
21. AmajoritydetectorhasthreeinputvariablesA,BandCandtwooutput light indicators.
Greenlight(G)willbeonifmajorityoftheinputvariablesareequalto1.Redlight(R)will
beonifmajorityoftheinputvariablesareequalto0.
(a) Constructatruthtableforyourdesign.
(b) ObtainlogicalexpressionsforGandR,respectively.
(c) DrawlogiccircuitimplementationsforGandR.
EG1108ElectricalEngineering~AdditionalProblemsforPart2
7
22. ProvethefollowingDeMorgan’slaw:
A B C A B C
23. Use theDeMorgan’s lawsandanyof first17 rulesofBooleanAlgebra toprove the last
rule,i.e.,Rule18:
A A B A B
24. Consideralogicalexpression
( ) ( )W A C B C
a) ConstructatruthtableforW.
b) UsetheKarnaughmaptechniquetosimplythelogicalexpression.
c) Implementthelogicalexpressionobtainedin(ii)usingonly2two‐inputNORgates.
25. AnLEDdisplaypanelshowninthefigurebelowhasfourLEDlightbarslabeledA,B,Cand
D, respectively.Youare required todesignanappropriatedigital logic circuit todisplay
LettersFandLusingthepanel.
(a) Constructatruthtableforyourdesign.
(b) ObtainlogicalexpressionsforFandL,respectively.
(c) Draw logic circuit implementations forF andLusingonly2‐inputNORgates (i.e.,
eachNORgateonlyhastwoinputchannels).Foreachletter,youcannotusemore
than8NORgatesfortheimplementation.
(d) WhatotherEnglishletterscanbedisplayedbythepanel?
26. Derivealogicalexpressionfortheswitchcircuitshowninfigurebelow.
EG1108ElectricalEngineering~AdditionalProblemsforPart2
8
27. ThetruthtablebelowshowstherelationshipbetweeninputsA,B,CandD,andoutputZ.
(a) FindZintermsofA,B,CandDintheSum‐of‐products(SOP)form.
(b) SimplytheexpressionobtainedusingKarnaughmap.
(c) Implement the logicalexpressionobtained in (b)usingnomore than4 two‐input
NORgates(i.e.,eachNORgateonlyhastwoinputchannels).
28. Amultiplexer is a device setting its single output to the same value as one of itsmany
inputs. Shown in the figurebelow is amultiplexerof two inputs, X andY, inwhichX is
selectedwhenthecontrolinputC=0andYisselectedwhenC=1.
(a) AssumethatbothXandYarelogicalvariables,constructatruthtablefortheabove
multiplexer.
(b) ObtainalogicalexpressionforZintheSOPform.
(c) UseKarnaughmaptosimplifytheexpressionofZobtainedinPart(b).
(d) Draw a logic circuit implementation for Zusing no more than 7 two‐input NOR
gates(i.e.,eachNORgateonlyhastwoinputchannels).
29. PrepareatruthtableforeachofthefollowingBooleanexpressions:
(a) F A B A B
(b) F A B C A B C A B C
EG1108ElectricalEngineering~AdditionalProblemsforPart2
9
30. WithoutusingKmaps,simplythefollowingBooleanexpressions:
(a) F A C C D B C D
(b) F A B C B C A B D B C D
31. UsingKmaps,simplytheBooleanexpressionsinProblem30.
32. DerivetheBooleanexpressionsforthelogiccircuitsshownbelow.
33. DrawthelogicdiagramforthefollowingBooleanexpressions,withoutsimplifications:
(a) F A B B C A B D A C D
(b) ( ) ( ) ( )F X Y X Z Y Z
(c) F A C B C A B C
(d) ( ) ( ) ( )F X Y X Z Y Z
34. RepeatProblem33withsimplification.
EG1108ElectricalEngineering~AdditionalProblemsforPart2
10
35. DerivetheBooleanexpressionsforthelogiccircuitsbelow.
36. Thelogiccircuitbelowisknownasaparitycheckerfora4‐bitbinarynumber.(a)Derive
itsBooleanexpression.(b)Prepareitstruthtable.(c)Canyourealizethesamefunctionby
usingfewerlogicgates?
37. Thelogiccircuitshownbelowisonepartofthemagnitudecomparatorusedtocompare
twobinarynumbers.(a)Prepareitstruthtable.(b)Canyoudescribethiscircuit?