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Optimisation of a transverse flux linear PM generator using 3D Finite Element AnalysisSchutte, Jacques 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Several transverse flux and longitudinal flux linear generator topologies exist for freepiston
Stirling engine applications. In this thesis the transverse flux permanent magnet
linear generators are investigated together with a back-to-back converter which can
deliver the electrical energy from the linear generator to the electrical network.
The transverse flux permanent magnet linear generator is geometrically optimised
with the aim to maximise the power-to-weight ratio while maintaining preset power
and efficiency levels. An optimised 3 kW linear generator is built and the measured
results correlate to the simulation results.
A close-loop current control scheme is introduced to control the current of the rectifier,
which is part of the back to back converter. The transverse flux permanent magnet
linear generator is connected to the input of the rectifier which has the ability to force
a specific current from the generator. The measured results of the rectifier correlate
to the results of the simulations that were done. The current control present some
complications and it is suggested that another control scheme is used.
A close-loop voltage control scheme is introduced for the control of the DC bus voltage.
The DC bus is connected between the rectifier and the inverter, which is the other
part of the back-to-back converter. A close-loop current control scheme is introduced
to control the inverter current that flows from the inverter to the electrical network.
The measured results of the inverter and the DC bus correlate to the results of the
simulations that were done.
The results of the system, including the generator, rectifier and inverter, tested as a unit
is presented and discussed. / AFRIKAANSE OPSOMMING: Verskeie tranverse vloed en longitudinale vloed lineˆere generator topologie¨e bestaan
vir vrysuier Stirling enjin toepassings. In hierdie tesis word ’n transverse vloed permanente
magneet lineˆere generator ondersoek saam met ’n omsetter. Die omsetter dra
die elektriese energie van die generator oor aan die elektriese netwerk.
Die transverse vloed permanente magneet lineˆere generator word geometries geoptimeer
met die doel om die drywing-tot-gewig verhouding te maksimiseer terwyl vasgestelde
drywing en effektiwiteit vlakke behou word. ’n Geoptimeerde 3kW lineˆere
generator prototipe is vervaardig en die gemete resultate is geverifieer met die simulasie
resultate.
’n Geslote lus stroombeheer strategie word voorgestel om die stroom te beheer van
die gelykrigter, wat deel is van die omsetter. Die transverse vloed permanente magneet
lineˆere generator word aan die gelykrigter, wat die vermo¨e het om ’n spesifieke
stroom uit die generator te forseer, se intree verbind. Die gemete resultate van die
gelykrigter wat gebou is stem goed ooreen met die van die simulasies wat gedoen is.
Die stroombeheer hou komplikasies in wat bespreek word. Dus word die gebruik van
’n alternatiewe stroombeheer voorgestel.
’n Geslote lus spannings beheer strategie¨e word voorgestel om die gs. busspanning
te beheer. Die gs. bus is gekonnekteer tussen die gelykrigter en die wisselrigter, wat
ook deel uitmaak van die omsetter. ’n Geslote lus stroom beheer word voorgestel om
die stroom te beheer wat vanaf die wisselrigter na die elektriese netwerk toe vloei. Die
gemete resultate van die wisselrigter en die gs. bus stem goed ooreen met die van die
simulasies wat gedoen is.
Die resultate van die hele stelsel, wat die generator, gelykrigter en die wisselrigter
insluit, wat as ’n eenheid getoets is word weergegee en bespreek.
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Optimum Design of Axial Flux PM Machines based on Electromagnetic 3D FEATaran, Narges 01 January 2019 (has links)
Axial flux permanent magnet (AFPM) machines have recently attracted significant attention due to several reasons, such as their specific form factor, potentially higher torque density and lower losses, feasibility of increasing the number of poles, and facilitating innovative machine structures for emerging applications. One such machine design, which has promising, high efficiency particularly at higher speeds, is of the coreless AFPM type and has been studied in the dissertation together with more conventional AFPM topologies that employ a ferromagnetic core.
A challenge in designing coreless AFPM machines is estimating the eddy current losses. This work proposes a new hybrid analytical and numerical finite element (FE) based method for calculating ac eddy current losses in windings and demonstrates its applicability for axial flux electric machines. The method takes into account 3D field effects in order to achieve accurate results and yet greatly reduce computational efforts. It is also shown that hybrid methods based on 2D FE models, which require semi-empirical correction factors, may over-estimate the eddy current losses. The new 3D FE-based method is advantageous as it employs minimum simplifications and considers the end turns in the eddy current path, the magnetic flux density variation along the effective length of coils, and the field fringing and leakage, which ultimately increases the accuracy of simulations.
After exemplifying the practice and benefits of employing a combined design of experiments and response surface methodology for the comparative design of coreless and conventional AFPM machines with cores, an innovative approach is proposed for integrated design, prototyping, and testing efforts. It is shown that extensive sensitivity analysis can be utilized to systematically study the manufacturing tolerances and identify whether the causes for out of specification performance are detectable.
The electromagnetic flux path in AFPM machines is substantially 3D and cannot be satisfactorily analyzed through simplified 2D simulations, requiring laborious 3D models for performance prediction. The use of computationally expensive 3D models becomes even more challenging for optimal design studies, in which case, thousands of candidate design evaluations are required, making the conventional approaches impractical. In this dissertation a new two-level surrogate assisted differential evolution multi-objective optimization algorithm (SAMODE) is developed in order to optimally and accurately design the electric machine with a minimum number of expensive 3D design evaluations.
The developed surrogate assisted optimization algorithm is used to comparatively and systematically design several AFPM machines. The studies include exploring the effects of pole count on the machine performance and cost limits, and the systematic comparison of optimally designed single-sided and double-sided AFPM machines. For the case studies, the new optimization algorithm reduced the required number of FEA design evaluations from thousands to less than two hundred.
The new methods, developed and presented in the dissertation, maybe directly applicable or extended to a wide class of electrical machines and in particular to those of the PM-excited synchronous type. The benefits of the new eddy current loss calculation and of the optimization method are mostly relevant and significant for electrical machines with a rather complicated magnetic flux path, such is the case of axial flux and of transvers flux topologies, which are a main subject of current research in the field worldwide.
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Analýza trojrozměrných objektů metodou konečných prvků v časové oblasti / Analysis of three-dimensional objects by time-domain finite elementsSyrový, Jiří January 2011 (has links)
This thesis is aimed on three-dimensional finite element time domain analysis. Vector finite elements are used for analysis of cavity resonator made from PEC and filled with vacuum. Results are compared with classical “nodal” finite elements and with published literature.
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