Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: The dielectric-barrier discharge (DBD) is a source of non-equilibrium plasma that has
seen widespread industrial application in recent years. A high-voltage arbitrary-waveform
generator has been designed, built and characterised for the purpose of investigating the
influence that the applied voltage waveform has on the operation of a DBD.
The developed arbitrary-waveform generator is based on the principle of Fourier synthesis.
Up to twenty Fourier components are generated by means of a digital circuit
board, and then separately amplified by Class-AB amplifiers. Twenty step-up transformers
are subsequently used to transform the Fourier components to higher voltages; the
summation of the Fourier components are realised by the series connection of the transformer
secondary sides.
It was found that the digital generation of the Fourier components is very accurate
and provides for the easy configuration of arbitrary waveforms. Furthermore, the amplification
of the Fourier components by the Class-AB amplifiers introduces very little
distortion. The principle of adding the Fourier components via the step-up transformers
has been demonstrated; however, the large distributed capacitances of the transformers
adversely affect the operation of the Class-AB amplifiers, leading to the introduction of
distortion into the generated waveform. Furthermore, it was found that care had to be
taken to limit the introduction of EMI through the system’s large ground plane. / AFRIKAANSE OPSOMMING: Die di¨elektriese versperringsontlading (DVO) is ’n bron van nie-ekwilibrium plasma wat
in die afgelope jare wye toepassing in die nywerheid gevind het. ’n Arbitrˆere-golfvorm
hoogspanningskragbron is ontwerp, gebou en gekarakteriseer, met die doel om die invloed
wat die aangewende spanningsgolfvorm het op die werking van die DVO, te ondersoek.
Die ontwikkelde arbitrˆere golfvormgenerator is gebaseer op die beginsels van Fourier
samestelling. Tot twintig Fourier komponente word digitaal gegenereer, en dan afsonderlik
versterk deur Klas-AB versterkers. Twintig transformators word dan gebruik om die
Fourier komponente na ho¨er spannings te transformeer. Die sommasie van die Fourier
komponente geskied deur die serieskakeling van die transformators se sekondˆere windings.
Daar is bevind dat die digitale generasie van die Fourier komponente baie akkuraat is,
en dat die arbitrˆere golfvorms maklik verstel kan word. Verder versterk die Klas-AB versterkers
die Fourier komponente sonder enige noemenswaardige vervorming. Die gebruik
van die transformators om die Fourier komponente saam te voeg, is gedemonstreer. Die
groot verspreide kapasitansies van die transformators be¨ınvloed egter die funksioneering
van die Klas-AB versterkers, wat lei tot ’n vervorming van die uittree. Daar is ook bevind
dat die toetrede van EM versteurings deur die grondvlak van die sisteem problematies
kan wees.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/19863 |
| Date | 03 1900 |
| Creators | Schwardt, Eckhard Detlef |
| Contributors | Rohwer, E.G., Stellenbosch University. Faculty of Science. Dept. of Physics. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xii, 109 leaves : ill. |
| Rights | Stellenbosch University |
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