Der Beitrag stellt Zweischicht-Bruchlochwicklungen mit einem Wickelschritt von zwei Nuten als einen m¨oglichen Kompromiss vor, welcher weniger ohmsche Verluste als bei klassischen verteilten Wicklungen und weniger Ummagnetisierungsverluste als bei Zahnspulenwicklungen ermöglicht. Er diskutiert Entwurf und Eigenschaften solcher Wicklungen f¨ur drei- und sechssträngige Synchronmaschinen anhand ausgewählter Beispiele. / This paper presents two layer fractional slot windings with a winding step of two slots as a possible compromise which enables less ohmic loss than classic distributed windings would have and less hysteresis and eddy loss than fractional slot concentrated windings would have. It discusses properties and design of such windings for three- and six-phase synchronous machines based on selected examples.

Heat transfer inside rotating coolant channels have a significant impact in design of gas turbine airfoils and other rotating components such as generator windings.  The effects of the Coriolis acceleration and centrifugal buoyancy have a significant impact on heat transfer behavior inside such rotating coolant channels due to the complex flow patterns of coolant.  Detailed heat transfer knowledge greatly enhances the designers\' ability to validate numerical models of newly designed channels. A rotating experimental rig was designed and built to model scaled up coolant channels at speeds up to 750 rotations per minute (rpm).  A camera is mounted onto the rotating test section and a transient liquid crystal technique is used to measure detailed heat transfer coefficients on a surface of interest.  The experimental set-up is innovative, as it involves no surface heating of the test section, very little instrumentation beyond a few thermocouples and a spray coating of thermochromic liquid crystals on the test surface.  To validate the test rig and the experimental method, multipass coolant channels with rib turbulators, large diameter radially outward channels with rib turbulators, and jet impingement cooling schemes are studied during rotation.  90deg, W, and M-shaped rib enhancements are studied and detailed heat transfer measurements clearly capture the heat transfer enhancement mechanisms with and without rotation.  Jet impingement schemes with single and double rows, normal and off-angle jets, and a cross flow outlet condition are all studied under rotation.  Non-rotating studies are also performed for baseline comparisons to rotating conditions.  Large aspect ratio, diverging channels with dimple and rib turbulators are studied in a stationary condition.  Results for all different test geometries show good comparisons with published studies indicating that the rotating rig and experimental method are valid.  Jet impingement schemes produce higher heat transfer compared to the two-pass channels with ribs, however pressure losses are significantly higher.  The fewer the jets and H/d=1 produces the highest pressure losses with no significant gain in heat transfer.  Off angle jets at H/d=1 produces very high pressure losses with no heat transfer advantage.  A final study with radially outward coolant channels is performed with the highest rotation speeds.  The structure, test section, and camera are thoroughly designed to withstand the exceptional g-forces.  Heat transfer in the radial channels with and without rotation show very little effect of rotation due to the small rotation number. / Ph. D.

Electrical machines have been widely used along the last decades with large life length under operating conditions. However, they will become more important in the upcoming years because of the emerging electric car industry. Thus, the maintenance cost of this technology can be reduced by extending the lifetime in the electrical machines. Despite the fact that existing numerous studies within the life length in these devices, only few study the effect of the thermomechanical stresses of insulation. The core of this master thesis is to study the influence of these stresses in the insulation material of a winding. The tested electrical machines were subjected to different test conditions, allowing to analyse multiple aging effects in the winding. To achieve these effects, power cycling tests were carried out on stators, where the windings were tested in cycles with different ΔT and two cooling methods: air cooling and oil cooling. The results showed large aging differences between the two cooling methods employed. The aging effect in the oil cooling method was higher than in the air cooling method for the same number of cycles. However, the aging effects regarding the same cooling process had not wide differences between the different test temperatures.

No description available.

Switched reluctance machines (SRMs) are well known for their simple and robust structure, facilitating their increasing application in many sectors, for example vacuum cleaners, where domestic machines operate at high-speed, 50,000 RPM being typical. Conventional SRMs (CSRMs) use a decoupled concentrated phase winding so that torque is predominantly only generated due to the self-inductance, which limits utilization of the machine electrical circuits. In this thesis, the toroidal winding SRM (TSRM) is introduced, which operates based on the variation of mutual inductance between different phases. The toroidal winding introduces additional winding space, and the winding is practically easy to implement, both features that lead to a relatively higher copper filling factor. The toroidal winding also benefits the machine thermal performance, as the winding is directly exposed on the machine periphery and thus accessible to cooling. All these make TSRMs interesting and meaningful for further study. Following a comprehensive comparison of CSRM and TSRM characteristics, a general torque equation is presented that is applicable to both CSRM and TSRM. Two 12-switch converters are proposed to drive three-phase TSRMs. Moreover, sinusoidal current excitation with a commercial three-phase half-bridge converter has been suggested as an alternative converter solution for TSRMs. Accordingly, a three-phase six-stator-pole, four-rotor-pole CSRM is designed and optimized with a speed of up to 50,000 rpm in this thesis. A TSRM is resized to achieve the same envelope dimension as a benchmark CSRM. Thus, a comparative study between high-speed CSRM and TSRMs has been carried out. They have both been prototyped and tested. The findings suggest that the TSRM is superior, considering machine mass and wire temperature management. The TSRM has a better torque output at lower speeds because copper losses are dominant. However, the CSRM has more advantages at higher speeds due to lower iron losses and lower DC voltage requirements. / Thesis / Doctor of Philosophy (PhD)

This thesis proposes innovative methods to extract information embedded in the frequency and time domain response of the transformer winding, and utilizes them to suggest solutions to a few tasks that have until now been thought difficult, if not impossible, to resolve. Pursuing this philosophy originated from the basic under- standing that the response of any physical system (behaving largely as a linear time invariant system) has embedded information that characterizes it completely. So, the prerequisite is to evolve ways to extract this information from measured responses. Once that is done, a variety of interesting applications can be envisaged. The two applications considered in this thesis are- •Investigate indirect measurement of the series capacitance of a transformer winding using the measured frequency or time domain response •Explore the possibility of increasing the physical resolution of the ladder network used to model a fully interleaved-disk winding In the former application, since direct measurement of series capacitance is impossible, alternatives based on indirect measurement were also not attempted. Similarly, in the latter application, the upper limit is known to be fixed by the number of distinctly observable peaks in the magnitude frequency response, so the question of increasing this limit was also never explored. Solutions to these tasks are proposed after a systematic analysis of frequency/time domain responses of a winding, initially modeled as a lumped parameter ladder network, to extract correlations that exist between them and winding parameters, and finally examine how these relations can be exploited together with the measured responses. Each of the five chapters is dedicated to describe the solution to one task. In each chapter, analytical formulation is presented first, followed by experimental results. Good agreement with the predicted results demonstrates its practicability. In final summary, indirect measurement of the series capacitance of a winding and en- hancing physical resolution of a ladder network model to represent a fully interleaved- disk winding was successfully demonstrated and they are the main contributions of this thesis.

Natural fibre composites (NFCs), which are polymers reinforced with cellulosic bast fibres, have the potential to be applied into a range of building products. They are seen as an alternative to glass fibre reinforced plastics (GFRP) in some applications, because of natural fibres (NF) relatively high strength and low density. Moreover, natural fibres have a set of beneficial traits, such as thermal insulation, thermal stability, biodegradability, and are inherently renewable. Those characteristics are of importance when NF are used as reinforcements in polymer composites, but developments in mechanical performance, reliability and economic viability are still required in order to be adopted fully by industry. The goal of this thesis was the development of a processing methodology for NFC laminate and subsequent material characterisation to assess the developed material suitability for building applications. Research objectives included materials selection, processing route development for laminates and tubes, manufacture of NFC laminates and analysis of mechanical properties in order to find an optimal composition. Hemp and flax fibres were selected as the reinforcement, because both have high mechanical properties and are important bast fibre crops in the European region with established cultivation and processing methods. As a matrix, fossil-fuel based and partially bio-derived thermoset resin systems were used. Handling and processing methodologies were developed for laminates and composite tubes based on filament winding and compression moulding techniques. The effects of the selected factors, namely material composition, volume fraction, processing parameters, reinforcement linear density, yarn twist, lamination sequence, yarn waviness and hybrid hemp-wool reinforcement were subsequently described in mechanical properties analysis of laminates. The influence of weathering conditions on the mechanical performance of the NFCs was examined. Furthermore, a study of NFC tubes under compression was performed. Results showed that the developed laminates reinforced with NF yarns have sufficient mechanical properties to be utilised in sandwich panels and/or tubes. However, a low resistance to moisture-related weathering restricts the developed NFCs for indoor applications.

<p>In this thesis, a concept for a modular assembly direct drive permanent magnetgenerator is presented. The maximum forces that act on the different parts of thegenerator during normal operation have been calculated and used in solid mechanicsimulations in SolidWorks. The result is a rough first draft of a generator designwhere the stator has been divided into five modules and the rotor into six modules.This division is done in order to avoid symmetries in the generator that could lead toproblems with self-oscillation.The modulization of the stator brings about certain difficulties, both for the magneticcircuit and for the winding scheme. Different solutions for optimization of themagnetic circuit are analyzed from both a physical and a construction technicalperspective. A winding scheme is produced and the winding process tested in awinding dummy produced according to the conceptual generator design.</p>

In this thesis, a concept for a modular assembly direct drive permanent magnetgenerator is presented. The maximum forces that act on the different parts of thegenerator during normal operation have been calculated and used in solid mechanicsimulations in SolidWorks. The result is a rough first draft of a generator designwhere the stator has been divided into five modules and the rotor into six modules.This division is done in order to avoid symmetries in the generator that could lead toproblems with self-oscillation.The modulization of the stator brings about certain difficulties, both for the magneticcircuit and for the winding scheme. Different solutions for optimization of themagnetic circuit are analyzed from both a physical and a construction technicalperspective. A winding scheme is produced and the winding process tested in awinding dummy produced according to the conceptual generator design.

In the field of electric machine design, a trend in many applications has been to design machines with increasing torque density. When machines fail to meet torque density requirements or are simply incapable of matching load torque, gears are commonly used. Magnetic gears have been proposed as a means of increasing torque density within electromechanical systems, while avoiding problems associated with traditional mechanical gears. While the idea behind magnetic gears goes back to early patents, their study and use in industry has been very limited to date. This study looks into variations of the gear which could lead to more industrial use. The effect of pole count upon torque ripple is investigated with finite element analysis (FEA). The analysis is extended to new magnetic layouts which borrow from permanent magnet machine design. One of the most critical components of the gear, the stator pole pieces, are also investigated for variations which aid in construction while maintaining the performance of the gear. As a means of supplementing analysis of the gear, winding function theory (WFT) is used to analyze the gear. Winding function theory has enjoyed success with induction, synchronous, and even switched reluctance machines in the past. This study is the first of its kind to apply winding function theory to a device devoid of windings altogether. It is shown that this method is capable of generating the stall torque and steady-state torque ripple waveforms which have been commonly attempted with FEA. While magnetic gears enjoy distinct advantages over mechanical gears such as inherent overload protection, they are not as torsionally stiff as their mechanical counterparts. As such, the use of damper windings for the purpose of stiffening the gear against transient oscillations is also investigated. Several competing designs are investigated for their performance, and a final design is studied which is capable of arresting transient oscillations in less than a second. In addition, a prototype has been fabricated and will be used to verify the analysis undertaken. The prototype is used to verify variations of the stator pole pieces as well as the inner rotor magnetic layout. A dynamometer has been assembled to test the performance of the prototype. A new design is also proposed for future work.