Thesis (MSc (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Knowledge of the magnetic fields in the domain of electrical machines is required in order
to model machines accurately. It is difficult to solve these fields analytically because of
the complex geometries of electrical machines and the non-linear characteristics of the
materials used to build them. Thus, finite element analysis, which can be used to solve
the magnetic field accurately, plays an important part in the design of electrical machines.
When designing electrical machines, the task of finding an optimal design is not simple
because the performance of the machine has a non-linear dependence on many variables.
In these circumstances, numerical optimisation using finite element analysis is the most
powerful method of finding optimal designs.
In this thesis, the work of improving an existing finite element simulation package, formerly
known as the Cambridge package among its users, and the use of this package in the
optimisation of electrical machine designs, is presented. The work involved restructuring
the original package, expanding its capabilities and coupling it to numerical optimisers.
The developed finite element package has been dubbed SEMFEM: the Stellenbosch Electrical
Machines Finite Element Method.
The Cambridge package employed the air-gap element method, first proposed by Razek
et. al. [2], to solve the magnetic field for different positions of the moving component
in a time-stepped finite element simulation. Because many new machine topologies have
more than one air-gap, the ability to model machines with multiple air-gaps is important.
The Cambridge package was not capable of this, but during the course of this work, the
ability to model machines with multiple air-gaps using the air-gap element method was
implemented.
Many linear electrical machines have tubular, axisymmetric topologies. The functionality
to simulate these machines was newly implemented because the original program was not
capable of analysing these machines. Amongst other things, this involved the derivation
of the coefficients of an axisymmetric air-gap element’s stiffness matrix. This derivation,
along with the original air-gap element derived by Razek et. al. [2] and the extension of
the method to the Cartesian coordinate system by Wang et. al. [29, 30], completes the
derivation of all two-dimensional air-gap elements. In order to speed the numerical optimisation process, which is computationally expensive,
parallelisation was introduced in two areas: at the level of the finite element simulation
and at the level of the optimisation program.
The final product is a more powerful, more usable package, geared for the optimisation
of electrical machines. / AFRIKAANSE OPSOMMING: Kennis van die magnetiese velde in die gebied van elektriese masjiene word benodig om
masjiene akkuraat te modelleer. Dit is moeilik om hierdie velde analities op te los as
gevolg die komplekse geometrieë van elektriese masjiene en die nie-lineêre karakteristieke
van die materiale wat gebruik word om hulle te bou. Dus speel eindige element analise ’n
belangrike rol in die ontwerp van elektriese masjiene omdat dit gebruik kan word om die
magnetiese veld akkuraat te bepaal.
Wanneer elektriese masjiene ontwerp word, is dit nie ’n eenvoudige taak om ’n optimale
ontwerp te vind nie omdat die werkverrigting van die masjien nie-lineêr afhanklik is van
baie veranderlikes. Onder hierdie omstandighede is numeriese optimering, tesame met
eindige element analise, die kragtigste metode om optimale ontwerpe te vind.
In hierdie tesis word die verbetering van ’n bestaande eindige element simulasie pakket,
wat onder gebruikers van die pakket as die Cambridge pakket bekend staan, en die gebruik
van hierdie pakket vir die optimering van elektriese masjiene, voorgelê. Die werk het die
herstrukturering van die oorspronklike pakket, die uitbreiding van die pakket se vermoëns
en die koppeling van die pakket aan numeriese optimeerders behels. Die ontwikkelde
eindige element pakket word SEMFEM genoem: die Stellenbosch Elektriese Masjiene
Finite Element Method.
Die Cambridge pakket het van die lugspleet element metode, soos oorspronlik deur Razek
et. al. [2] voorgestel, gebruik gemaak om die magnetiese veld vir verskillende posisies
van die bewegende komponent in ’n tyd-stapsgewyse eindige element simulasie op te los.
Omdat baie nuwe masjien topologieë meer as een lugspleet het, is die vermoë om masjiene
met meer as een lugspleet te kan modelleer belangrik. Die Cambridge pakket was nie hier
toe in staat nie, maar die vermoë om masjiene met meervoudige lugsplete te modelleer is
gedurende hierdie werk geïmplementeer.
Baie lineêre masjiene het tubulêre, assimmetriese topologieë. Die funksionaliteit om hierdie
masjiene te simuleer is nuut geïmplementeer omdat die oorspronlike program nie in
staat was om hierdie masjiene te analiseer nie. Dit het onder andere behels dat die koeffisiënte
van ’n assimmetriese lugspleetelement se styfheidsmatriks afgelei moes word. Hierdie
afleiding, tesame met die oorspronlike lugspleetelement afgelei deur Razek et. al. [2]
en die uitbreiding na die Cartesiese koördinaatstelsel deur Wang et. al. [29, 30], voltooi
die afleiding van alle twee-dimensionele lugspleet elemente.
Om die numeriese optimeringsproses, wat tipies tydsgewys duur is, te versnel, is parallellisering
op twee vlakke ingebring: op die vlak van die eindige element simulasie en op die
vlak van die optimeringsprogram.
Die finale produk is ’n kragtiger, meer bruikbare pakket, goed aangepas vir die optimering
van elektriese masjiene.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6635 |
| Date | 03 1900 |
| Creators | Gerber, Stiaan |
| Contributors | Strauss, J. M., Randewijk, P. J., University of Stellenbosch. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 129 p. : ill. |
| Rights | University of Stellenbosch |
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