ENGLISH ABSTRACT: This thesis is a description of how the first magnetically geared axial flux permanent magnet generator
(MGAFG) is designed, constructed and experimentally evaluated. Magnetic gears (MGs) allow for
contact-less power transfer and lubricant free operation, which may solve the reliability concerns with
current mechanically geared wind energy converters.
However, the complex structure of MGs may present serious challenges to its design. Thus, special
care should be given to the mechanical layout and the electromagnetic influence of every component.
The MGAFG can be configured to be magnetically coupled or decoupled. In the coupled configuration
the permanent magnets (PMs) of the MG contribute to the total flux linkage in the PM generator
(PMG). The coupled configuration is therefore more efficient. The processing time required to optimise
the decoupled configuration is however much faster, since the MG and the PMG can be optimised
separately.
The optimised results show that a torque density in excess of 100kNm/m3 could be achieved, which
is significantly higher than any of known electrical machines. However, owing to excessive losses in the
mechanical support structures, the prototype exhibited lower torque density and poor efficiency. The
design related aspects and issues are analysed and discussed in detail in an attempt to outline problem
areas in the design process. Relevant recommendations are also given for future design improvements.
The costs of magnetic material accounts for over fifty percent of the total cost of the prototype. Therefore
to make the manufacturing of the MGAFG more economically viable magnetic material should be
minimised in the design process.
AFRIKAANSE OPSOMMING: In hierdie tesis word die eerste magnetiese geratte aksiale vloed permanente magneet generator
(MGAVG) ontwerp, vervaardig en eksperimenteel geëvalueer. In magnetiese ratte (MR) is daar geen
kontak tussen werkende dele nie, daarom word geen smeermiddels benodig nie. Dit dra by tot die
betroubaarheid van die ratkaste in wind energie generators en kan onderhoud grotendeels uitskakel.
Die komplekse struktuur van magnetiese ratte kan egter die betroubaarheid van die ontwerp juis
verswak. Daarom moet die meganiese uitleg noukeurig beplan word sodat dit nie die elektromagnetiese
werking ondermyn nie.
Die magnetiese rat (MR) en die permanente magneet generator (PMG) van die masjien kan magneties
of sonder magnetiese koppeling verbind word. In die gekoppelde konfigurasie dra all die permanente
magnete van die MR gesamentlik by tot die totale vloed-koppeling in die PMG. Wat die magnetiese
gekoppelde konfigurasie meer doeltrefend maak. Minder tyd word benodig om die nie magnetiese
gekoppelde konfigurasie te optimaliseer omdat die MR en die PMG apart geoptimaliseer kan word.
Die optimale resultate toon dat ’n wringkrag van meer as 100kNm/3 bereik kan word, wat aansienlik
beter is as die van bekende elektriese masjiene.
Maar as gevolg van oormatige verliese in die meganiese strukture, toon die prototipe lae wringkrag
digtheid en swak doeltreffendheid. Die ontwerp probleme word ontleed en bespreek in ’n poging
om probleem areas in die ontwerp te identifiseer. Relevante aanbevelings word gegee vir toekomstige
ontwerp verbeterings.
Die koste van die magnetiese material verteenwoordig meer as vyftig persent van die vervaardigings
koste van die prototipe. Koste kan bespaar word op die vervaardiging van die MGAVG deur die
hoeveelheid magnete wat gebruik word te beperk.
