Development of high efficiency high speed permanent magnet generator

Renewable energy technology is steadily gaining importance in the energy market because of the limited nature of fossil fuels, as well as the political pressures to reduce carbon emissions. To ensure sustainable development, adequate and affordable energy should be made available to satisfy the demand of electric energy. The High Speed Permanent Magnet (HSPM) generator is designed and developed and is expected to deliver 10 kW output power as well as to achieve a speed of 30000 RPM, however, to achieve a compact and efficient design with lower excitation losses, magnetizing currents and rotor losses requires the HSPM generator to be operated at high rated speeds of approximately 30000 RPM. However, at high speeds these machines produce a substantial amount of heat. This makes the thermal management of these machines difficult and complicated, which leads to demagnetization and the reduction of the output power and shortens the lifetime of the critical components such as the bearings. This thesis presents the design and development of the HSPM generator. It also identifies the heat generated by means of electromagnetic, mechanical and core losses. The development of an adequate cooling system (cooling jacket) is presented to avoid hot spots in the generator and thermal damage to the magnets, resulting in demagnetization. The use of pressurized oil air particles as a lubrication method for the bearings of the generator is also considered to avoid: thermal damage and starvation at the rolling element and to address the predominant concern of effectively cooling the HSPM generator ball bearings at elevated speeds. The HSPM generator is designed and developed to operate at a maximum speed of 30000 RPM to deliver 10 kW output power and is subjected to 80~92°C temperature rise with an idle power consumption of ~2kW, enough to cause hot spots on the generator, demagnetization of the magnets and severe impact to the rolling elements of the bearings. The developed cooling jacket and the newly developed oil air mist lubrication arrangement enables the control of the temperature rise of the generator and the temperature rise at the rolling element, respectively. A steady state analysis was also carried out at motor maximum power output to determine its safe operation with the objective of finding an optimal operating condition by performing a parametric study on the effect of cooling. A 3D steady state model of a 10-kW electric permanent magnet machine was generated and investigated with one cooling jacket layout. The end windings and bearings were not considered to simplify the motor model. Numerical analysis is performed with two different coolant flow rates, no flow and maximum flow (3.5 m3 /h) with special emphasis on the maximum motor temperature. The analytical calculations for the role of coolant flowrate on heat transfer characteristics for a high speed generator, showed that the convection heat transfer coefficient increases with an increase in flowrate (0.3 – 3.5 m3 /hr), while the numerical simulations showed that the maximum coolant flowrate conditions achieved lower temperature generation (27.9°C at the front bearing) throughout the generator compared to no coolant flowrate (43.7°C at the front bearing). The detailed understanding of the effects of these parameters on the generator’s temperature field will help in validating the performance of the generator with actual results

The propagation circuits for magnetic bubble-domain devices

Imperial Users onl

Magnetic antiperovskite Mn3AN thin films

As computing demands increase exponentially, so too has the desire for new computing technologies that operate faster and with greater efficiency. Ferromagnetic materials were initially seen as ideal candidates for use in memory and logic devices, and this field of study was termed “spintronics”. Subsequently many issues with using ferromagnets for this purpose have been discovered. They have high energy requirements for write operations, are sensitive to magnetic fields, and they produce stray fields which limit how densely elements may be packed together. Because of these challenges, interest has turned to antiferromagnetic materials (AFMs) which do not possess sensitivity to magnetic field, may be packed densely together, have multi-level stability, and have theoretical switching speeds 100 times faster than ferromagnets. These advantageous features bring the added complication that characterising AFMs, in particular thin films suitable for use in ICT, is notoriously challenging due to the vanishing magnetisation. In this thesis, we grow and investigate thin films of the antiperovskite family Mn3AN, where A = Ni, Sn. These materials possess particular non-collinear antiferromagnetic structures that lead to anomalous physical properties not normally expected in AFMs. We first look at the anomalous Hall effect (AHE), and show how strain applied using a piezoelectric substrate may be used to manipulate the intrinsic contributions to the AHE in Mn3NiN. We then use a scanning laser to induce a local thermal gradient in a patterned device, and by measuring the anomalous Nernst effect we reveal the underlying antiferromagnetic macrodomain distribution. Finally, we measure the MOKE spectra of a Mn3NiN sample for selected temperatures cooling through the Néel temperature, TN, and from comparisons with theory confirm the presence of a ferrimagnetic phase above TN. This phase shares the same magnetic space group as the non-collinear phase, and shows promise for spintronic applications at room temperature.Open Acces

Phase-field modeling of multi-domain evolution in ferromagnetic shape memory alloys and of polycrystalline thin film growth

The phase-field method is a powerful tool in computer-aided materials science as it allows for the analysis of the time-spatial evolution of microstructures on the mesoscale. A multi-phase-field model is adopted to run numerical simulations in two different areas of scientific interest: Polycrystalline thin films growth and the ferromagnetic shape memory effect. FFT-techniques, norm conservative integration and RVE-methods are necessary to make the coupled problems numerically feasible

Thin-Film Ferrofluidics

We study dynamics of ferrofluids in thin-film configurations. We first spend a considerable amount of time deriving a basic model to describe the flow in a limiting case. We then investigate the magnetization in the fluid, formulate a differential equation governing the curvature of the boundary, then finally study a pressure Poisson equation with a moving boundary

Design and Application of Electrical Machines

Electrical machines are one of the most important components of the industrial world. They are at the heart of the new industrial revolution, brought forth by the development of electromobility and renewable energy systems. Electric motors must meet the most stringent requirements of reliability, availability, and high efficiency in order, among other things, to match the useful lifetime of power electronics in complex system applications and compete in the market under ever-increasing pressure to deliver the highest performance criteria. Today, thanks to the application of highly efficient numerical algorithms running on high-performance computers, it is possible to design electric machines and very complex drive systems faster and at a lower cost. At the same time, progress in the field of material science and technology enables the development of increasingly complex motor designs and topologies. The purpose of this Special Issue is to contribute to this development of electric machines. The publication of this collection of scientific articles, dedicated to the topic of electric machine design and application, contributes to the dissemination of the above information among professionals dealing with electrical machines