DTIC ADA542381: Evaluation of Thermal Voltage Converters Low-Frequency Errors

6 Pages·0.06 MB·English

by  Defense Technical Information Center

.
Session 2259
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email: [email protected]
Abstract: This paper describes a student independent research project. The project task was to
etaulave eht wol ycneuqe rsfrorre fo lamreh Tega tslroeVtre v.n)osCCVT( A dohtem ot etaulaveeht
w oylcne usqreorrfre fo sCVT sah n edeebpoleve d[( ,]1 .)]2[ sihT dohtem si desabs tnnoemerusaem
of the dc transfer function and time constant of the tested TVC. The error analysis is performed in
the frequency domain. The first phase of the student project was to confirm the developed method
yb gnitar eBnA eLngToAiMtalu mdiessab no eshntoitacil b]ulp[ dna .]2[ ehT s’tcej odrnpocesesahp
was to analyze the TVC errors in the time domain and compare the results.
NOITCUDORTNI
At the United States Naval Academy students have the opportunity to engage in research projects
throught hec oursec alledi ndependentr esearchs tudy.I ti so fferedt ot hef ourthy ears tudentsa ndi t
roetinlhsgate otro iee ndsg e aerfftcafhhcooe urmf ltwe tsomiy nbs deI ertrso f.pu plo rtutnfhioetry
interested students to obtain some research experience and it provides students prospective to the
ytluca f.rebmem yreV netfo eht hgih level hcraeser si yaw dnoy e.sbn’otinsendeuhtgesnripvmaoHc
motivated student engaged in a project results in the focus on fundamentals. Through these
discussionsm osto ft het imeb otht hes tudenta ndt het eacherb enefit.
CVTSLATNEMADNUF
TVcCo nsistosraf e sistorR,a, n tadh ermoelemen(tT Ec)o nnecteidsn e riesT.h ree sistolri mittsh e
current, I, through the TE. A TE consists of a low resistance heater to which a temperature sensor
si .dehcatta ehT rosnes si yllareneg aelpuocom rteahhtt secudorp a llams etvuipttoumoo,retccreolfe
E proportional to the heater temperature. The heater temperature is proportional to the input
,fme
rew oPp =I 2 .R fI eedhuttil pfmoa e hdteilpp aC Aegatlo vstinats ndonca st idoirep si ldlearmaspmoc
to the time constant of the TE, the heater temperature and the output E , are constant. TVCs are
fme
used in this operating mode as ac-dc converters.
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1. REPORT DATE 3. DATES COVERED
1998 2. REPORT TYPE 00-00-1998 to 00-00-1998
4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER
Student Independent Research Project : Evaluation of Thermal Voltage
5b. GRANT NUMBER
Converters Low-Frequency Errors
5c. PROGRAM ELEMENT NUMBER
6. AUTHOR(S) 5d. PROJECT NUMBER
5e. TASK NUMBER
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
United States Naval Academy,Department of Weapons and Systems REPORT NUMBER
Engineering,Annapolis,MD,21402
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)
11. SPONSOR/MONITOR’S REPORT
NUMBER(S)
12. DISTRIBUTION/AVAILABILITY STATEMENT
Approved for public release; distribution unlimited
13. SUPPLEMENTARY NOTES
ASEE Conference Proc., Seattle, Washington, 1998
14. ABSTRACT
This paper describes a student independent research project. The project task was to evaluate the low
frequency errors of Thermal Voltage Converters (TVCs). A method to evaluate the low frequency errors of
TVCs has been developed ([ 1], [2]). This method is based on measurements of the dc transfer function and
time constant of the tested TVC. The error analysis is performed in the frequency domain. The first phase
of the student project was to confirm the developed method by generating MATLAB simulation based on
the publications [l] and [2]. The project?s second phase was to analyze the TVC errors in the time domain
and compare the results.
15. SUBJECT TERMS
16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF
ABSTRACT OF PAGES RESPONSIBLE PERSON
a. REPORT b. ABSTRACT c. THIS PAGE Same as 5
unclassified unclassified unclassified Report (SAR)
Standard Form 298 (Rev. 8-98)
Prescribed by ANSI Std Z39-18
I
heat through radiation and along its input leads. Since the loss is greater at higher temperature the _
0
-1 5
0 01 02 03 04 0.5 06 0.7 08 09 1
(Time [s]
erugiF.1 Comparison between measured output E -o-, and input voltage squared, -x-.
fme
LEDOM
tesheTl pymaiws ot ledo meht rCoViTva hseib roetdis ntoic ot eb eh tts rriefdr owol s.sraeptleihfT
frequency response of this filter is then used to scale the dc transfer function. The model performs
eht gniwollof:snoitcnuf
1. serauqS a dleatdailo ustmuuinp sinesigatlov dna sretlif ti gnisu a wol ssap retlif htiw a tucffo
ycneuqefrf =1/(2n7:), where t is the TVC time constant.
c
2. Calculates the peak to peak variation, varpp(f), at the filter’s output for a particular
ycneuqerf htiw tupni egatlov V.deilppa
3. Calculates the average output emf ta a yrev wol ycneuqerf erehw( eht gnikcart srorreera
fl
)mumixam htiw tupni egatlov V.deilppa
4. Calculates the output emf ta a ecnerefer ycneuqerf erehw( gnikcart srorre era)elbigilgen
fer
htiw tupni egatlov V.deilppa
tA ycneuqerf ,f eht detamits ecd- ceacne r)eff(faiddbmal si detalucl:agcnisu
where n is the power exponent that describes the transfer function of the TVC [I].
Programing this procedure was the first task the student performed. Measured TVC’s transfer
function and its time constant were given and the obtained results were compared to independently
measured ac-dc differences. Since the performance of this approach has been already demonstrated
[l, 2], this task was not very difficult and it was executed smoothly (see Fig. 2).
,
erugiF.2 nosirapmoC neewteb ,detalumis ,-o- dna ,derusaem ,-*- CDCA.secnereffid
EMIT NIAMODSISYLANA
Ideally the TVC transfer function should be the parabola (input voltage squared). However,
practically the power coefficient needs to be calculated for each value of the input voltage. For the
given transfer functions the student calculated power coefficient (see Fig 3.). The range of
,stneicif fhetoicw eh tet a,inropiotruplpoas eerrew nevig dna eht margorp dekcip eht tseb tif rofhcae
measurevda luoetf h ien puvto ltageI.it ns o eta stymo e asurteh TeV tCr ansfefru nctiosni ncteh ere
is significant temperature drift. Practically, it is possible to measure the TVC transfer function for
about hundred input voltage values in the TVC’s optimal range of operation. Since we were
interested in better input voltage resolution it was necessary to fit a polynomial curve using the
calculated power coefficient. This has proven not to be the trivial task. Since the power coefficient
noncnieu-cwssicrplduae tnevaiirsgfhitsernfv mtietos asefeeot aneae n srd rrtey esg n mtwe intths
appropriate polynomial order. It was an iterative process to arrive to the best fit (see Fig 4).
Then exts tepw ast or econstructt heT VCo utpute mf.O nei deaw ast ou set hel owp asf iltero utput
voltage and apply appropriate power coefficient so that output emf could be generated. In order to
erapmoc eht stluser fo s inhotitalumi sot eht sltanuetmcearu seahetm egarev aeulav fo eht tuptuofme
has to be calculated. This part of the project was the most difficult. The simulation was developed
in MATLAB and special care has to be exercised when dealing with data vectors. Even after all of
the bugs were cleaned the results were not satisfactory since the ac-dc errors calculated with this
method were not comparable to the actual measurements.
erugiF.3 K values vs. input voltage. erugiF.4 .se ur tlolKiafafvimonyloP
S’TNEDUTSEVITCEPSORP
Therew aso nes tudentw orkingo nt hisp rojectf oro nes emester.I nt hef irstp haseo ft hep rojectt he
tneduts daer rebmun fo srepap dna ew dah gsnnooliss utcusoi bdganiledom e hsteitrepor pfolamreht
voltage converters. This project has elements of systems identification, transfer function
,s tyncenmeeu rqnuei sra, afms,eoigmdsnyilraentali fsa llew sa scisyhp no lamreht dna egat.lsotvceffe
The student was very excited to participate in integration of the number of concepts covered in
nonr-selyaislnt eeaamrw .cs oliramiksunoisltfnrao got oimo n
Student comments:
A great deal of learning process involved the actual computer programing and working out all of
thien tricacieotsfha el gorithms....Seeincgl assrootmo picasp pliegdas vmaeee n steh atth erweaa s
ttu“honelestsfnngi ehaar maeodagnenteetlfI vhs dit ” nete sr .fo lasdecp.iaate dbIric o. notu n,t.
the complexity of the trials and errors of the research process. I gained a whole new respect for
research in general. When I read the paper now I feel I can appreciate the extensive time and effort
thatg oesi ntod evelopingi ta ndt hem otivationr equiredb yt hep rofessionalw how ritet hem.G iven
the opportunity I would like to do this again one day.
SNOISULCNOC
Studenitn dependenrte searcphr ojectteo v aluatteh TeV lCo fwr equenceyr rorwsa psr esentedT.h e
project had two phases. The first phase was to research the subject of TVC and repeat already
detar thscnroameesder [ ,1 .12 ehT dnoces esahp saw ot tpmetta ot etalucla cs’CVT cd-ceacnereffid
by estimating transfer function power coefficients for each value of input voltage. The second task
has never been attempted before and presented the serious effort on the student’s part. It was real
egnellahc rof eht tneduts ot eb degagne ni tra - eehhhcttr-afeos-eert adtnsa ti saw la enroitavitomrof
the teacher to lead the true open ended project with the undergraduate student.
:secnerefeR
]1[ .N .M ,mahdlO .M .E rekraP dna .S ,civorumaZ-vomarvA gnirolpxE“ ehtycneuqerF-woL
Performance of Thermal Converters Using Circuit Models and a Digitally Synthesized
Source”, IEEE Transactions on Instrumentation and Measurement, Vol. 46, No. 2, April
.7991
.S ,civorumaZ-vomarvA .N .M ,mahdlO .M .E rekraP dna .B ,pirtlaW woL“ycneuqerf
Characteristics of Thin-Film Multijunction Thermal Voltage Converters”, accepted for
publication in IEEE Transactions on Instrumentation and Measurement.
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