| Summary: | Thesis (MScEng)--University of Stellenbosch, 2001. === ENGLISH ABSTRACT: This thesis describes the study of two soft-switching inverter topologies that are well suited to
high-power applications. For the first topology, namely an active resonant turn-off snubber,
the existing theory is expanded with a detailed study into operation strategies and topology
protection.
This is followed by an investigation into the second topology, which is a combined snubber
that reduces both turn-off and turn-on losses. The investigation involves a detailed analysis of
the losses in the snubber components and main devices, as well as a study into the effects of
parasitic components and diode reverse recovery on the operation of the snubber. Based on this
theory a snubber optimisation procedure is also developed. Possible operation strategies and
protection techniques were also evaluated for this topology. Single-phase experimental inverters
were used to verify the basic operation theory and switching loss prediction for both topologies.
The thesis is concluded by the design and construction of a practical soft-switching threephase
inverter. After implementation the experimental inverter is used for theory verification. === AFRIKAANSE OPSOMMING: Hierdie proefskrif beskryf die ondersoek na twee saggeskakelde omsetter topologieë wat veral
geskik is vir hoë-drywing toepassings. Die bestaande teorie aangaande die eerste topologie,
naamlik 'n aktiewe, resonante, afskakel gapser, word uitgebrei met 'n deeglike-studie oor bedryfstegnieke
en beskermingsmetodes.
Vervolgens word 'n gekombineerde gapser topologie, wat beide aanskakel- en afskakelverliese
verminder, ondersoek. Die studie behels 'n volledige analise van die verliese in die omsetter
en gapser komponente en die invloed van parasitêre komponente en diode tru-herstel. Hierdie
teorie word ook gebruik om 'n optimale gapser ontwerp prosedure te ontwikkel. Die moontlikke
bedryfstegnieke en beskermingsmetodes word ook vir hierdie topologie evalueer. In albei gevalle
is eksperimentele, enkelfase omsetters gebruik om die teorie oor basiese werking en skakelverlies
vermindering te verifieer.
Die ondersoek word afgesluit deur die ontwerp en konstruksie van 'n praktiese, saggeskakelde,
drie-fase omsetter te beskryf. Na implimentering van die omsetter word volledige eksperimentele
verifikasie uitgevoer.
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