Thesis (M.S.) in Electrical Engineering--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaf 49).

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No description available.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (p. 240-266). Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 151-164). Also available in print.

Thesis (MScEng)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: This thesis deals with the design and evaluation of a 300 kW double stage axial-flux permanent magnet generator with an ironless stator. The magnetic and electrical design equations are derived for sinewave and quasi-squarewave axial-flux permanent magnet machines. The thermal design approach used is also described. The machine is optimised for maximum torque per current loading. A Matlab program code is developed to do the necessary calculations in the design optimisation and the calculation of the machine parameters. Mechanical finite element simulations are conducted to investigate the severity of the magnetic attraction force between the rotor discs. The results obtained from the simulations suggested an increase in the yoke thickness in order to withstand the attraction force. The construction of the prototype machine's rotor and stator is described. The flux density in the airgap is thoroughly investigated through measurements and analysis. Thermal measurements are also conducted to investigate the effect of eddy currents in the stator winding. Furthermore, no-load measurements conducted on the 300 kW machine showed that the machine has a serious problem of circulating currents in the parallel connected coils. Possible solutions for this are investigated and recommendations are given. Due to the circulating current problem and the relative high eddy current losses, it was not possible to do full-load tests on the machine. / AFRIKAANSE OPSOMMING: Hierdie tesis handeloor die ontwerp en evaluering van 'n multi-stadium Aksiale Vloed Permanente Magneet (AFPM) masjien met 'n ysterlose stator. Die magnetiese - en elektriese ontwerp-vergelykings is afgelei vir sinusgolf en quasi vierkantsgolf AFPM masjiene. Die termiese ontwerp word ook bespreek. Die masjien is geoptimeer vir maksimum draairnoment per stroombelasting. Daar is 'n program-kode in Matlab geskryf om die nodige berekeninge vir die optimering van die masjien uit te voer en vir die bepaling van die masjien-parameters. Meganiese eindige element berekenings is gedoen om die invloed van die magnetiese aantrekkingskrag tussen die rotorskywe te ondersoek. Die resultate het aangedui dat die rotorskyfdikte nie die magnetiese aantrekkingskrag van die magnete kan weerstaan nie en moes in dikte vedubbel word. Die konstruksie van die masjien se rotor en stator is behandel. Die vloeddigtheid in die luggaping is noukeurig ondersoek deur metings en analise. Termiese metings is ook gedoen om die invloed van die werwel strome in die statorwikkelings te ondersoek. Verder het die nullas-toetse wat gedoen is op die masjien, aangedui dat die masjien 'n ernstige probleem het met sirkuierende strome in die parallelle geleiers van die statorspoele. Moontlike oplossings is ondersoek en aanbevelings word gegee. Dit was nie moontlik om vollastoetse op die masjien te doen nie, as gevolg van die probleem met sirkuierende strome en die relatiefhoë werwelstoom-verliese in die statorwikkelings.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This thesis presents a study on core loss calculations in rotating electrical machines. The basic concepts concerning magnetic moments, ferromagnetism, magnetic domains and magnetic hysteresis are introduced. The three-term models for alternating and rotational core losses in electrical steel sheets are presented. Several core loss measurement techniques are reviewed and an experiment is carried out to measure the total core losses in an electrical sheet steel sample under alternating and rotational magnetic fields of various frequencies and amplitudes. The coefficients in the loss models for alternating and rotational core losses are obtained through curve fitting process. The theory of electromagnetic fields is presented through the Maxwell equations and field scalar equations. A detailed review on core loss models for rotating electrical machines is presented. A rotational core loss model is adopted to calculate the core losses in a PM motor. The total core loss in the PM motor is obtained by summing the element losses using a MATLAB program. An experiment is conducted to measure the total core loss in the PM motor. The calculated total core loss in the PM motor is compared with the experimental results. The calculated total core losses are about 19% lower than the tested results. Various possible causes for this discrepancy are discussed / Master of Engineering (Hons)

Many high performance drive applications require wide Constant Power Speed Range (CPSR) for efficient use of energy. The examples of such applications are the starter alternator system of automobiles proposed for the 42V PowerNet, traction in the hybrid/electric vehicle, wind power generator etc. The Permanent Magnet (PM) machine is the natural choice of such niche applications because of their higher efficiency and compact size. However, the Surface Permanent Magnet (SPM) machine with sine distributed winding and radially-laminated Interior Permanent Magnet (IPM) machine with conventional structure has very limited or zero flux-weakening capability. The flux-weakening capability of the SPM machine can be improved by using concentrated, fractional-slot stator but here well-known advantages of the sine distributed winding are needed to be compromised. In the IPM machine, fluxweakening was improved using axial lamination and more than two magnet layers per pole. However, the construction of such IPM machine is complicated and expensive. This thesis presents design and analysis of a new type of the Interior Permanent Magnet (IPM) machine that have a very wide Constant Power Speed Range (CPSR) without compromising simplicity of construction and advantages of the distribution winding. In the new IPM machine, the magnet poles were segmented in the radially direction and the iron bridges between magnet segments provide for additional paths of flux-canalization to give the rotor an inherent capability of fluxweakening. Consequently, a very wide constant power speed range can be achieved in such machines. The proposed IPM machine of this work was referred as the Segmented IPM machine. The thesis focuses on the optimization of the Segmented IPM machine in a 42V environment of the automobile. First, for the conceptual evaluation a 4 pole, 550W Segmented Magnet IPM machine was optimized using finite element analysis. The parameters were calculated for prediction of the steady-state and transient performances. The torque- and power-speed capability were estimated using time-step, circuit-coupled finite element analysis. The cogging torque and variation of iron loss with frequency were also investigated during the design process. A prototype machine was constructed on the basis of the optimized design. The steady-state and transient performances of the prototype machine were measured and compared with the predicted results for experimental verification. The measured performance analysis was found to match very well with the predicted results. The measured torque- and power-speed capability of the Segmented IPM machine was also compared to those of a conventional, non-segmented IPM machine of similar rating and size. The thesis also presents the optimized design of a 6kW, 12 pole Segmented Magnet IPM machine for application in the Integrated Starter Alternator (ISA) of the electric/hybrid vehicle. It can be concluded from the predicted steady-state analysis of the 6 kW, 12 pole Segmented Magnet IPM machine that it should be able to satisfy most of the required criteria of an ISA with appropriate design optimization.