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

Studies in Electrical Machines & Wind Turbines associated with developing Reliable Power Generation

The publications listed in date order in this document are offered for the Degree of Doctor of Science in Durham University and have been selected from the author’s full publication list. The papers in this thesis constitute a continuum of original work in fundamental and applied electrical science, spanning 30 years, deployed on real industrial problems, making a significant contribution to conventional and renewable energy power generation. This is the basis of a claim of high distinction, constituting an original and substantial contribution to engineering science

Thermal analysis and air flow modelling of electrical machines

Thermal analysis is an important topic that can affect the electrical machine performance, reliability, lifetime and efficiency. In order to predict the electrical machine thermal performance accurately, thermal analysis of electrical machines must include fluid flow modelling. One of the technologies which may be used to estimate the flow distribution and pressure losses in throughflow ventilated machines is flow network analysis, but suitable correlations that can be used to estimate the pressure losses in rotor ducts due to fluid shock is not available. The aim of this work is to investigate how the rotation affects the pressure losses in rotor ducts by performing a dimensional analysis. Apart from the additional friction loss due to the effects of rotation, other rotational pressure losses that appear in a rotor-stator system are: duct entrance loss due to fluid shock and combining flow loss at the exit of the rotor-stator gap. These losses are analysed using computational fluid dynamics (CFD) methods. The CFD simulations use the Reynolds-averaged Navier Stokes (RANS) approach. An experimental test rig is built to validate the CFD findings. The investigation showed that the CFD results are consistent with the experimental results and the rotational pressure losses correlate well with the rotation ratio (a dimensionless parameter). It shows that the rotational pressure loss generally increases with the increase in the rotation ratio. At certain operating conditions, the rotational pressure loss can contribute over 50 % of the total system loss. The investigation leads to an original set of correlations for the pressure losses in air ducts in the rotor due to fluid shock which are more suitable to be applied to fluid flow modelling of throughflow ventilated machines. Such correlations provide a significant contribution to the field of thermal modelling of electrical machines. They are incorporated into the air flow modelling tool that has been programmed in Portunus by the present author. The modelling tool can be integrated with the existing thermal modelling method, lumped-parameter thermal network (LPTN) to form a complete analytical thermal-fluid modelling method

Partial discharge inception voltage in turn-to-turn insulation systems: modelling and uncertainties

In the late 19th century, the extraordinary inventors and pioneers Nikola Tesla, Thomas Edison, and George Westinghouse dreamed of transforming the world. After more than a hundred years since then, electricity has not stopped growing and is set to become the largest industrial system created by humanity. The democratization of hybrid and electric cars, and even more the future electrification of the aeronautical industry are signs of its unstoppable evolution. As a system in constant improvement and evolution, it has not been without challenges to overcome without compromising its reliability. One of the phenomena that continues to be a threat and reduces the reliability of machines are partial discharges. These events affect the insulation system and can cause a material failure that can translate into equipment damage, power supply interruption and even incendiary and explosive events. One of the cornerstones that this electrical system relies on is alternating current motors. Spurred on by progress in semiconductors and the discovery of the microprocessor, aging of DC motors have taken over. Since then, the electronic control of these motors has become essential, to the point that for small power rated machines, a single set is sold: “copper, iron and silicon”. Unexpectedly, this improved speed control caused a significant reduction in the reliability of the motors, causing unforeseen failures in the insulation systems. Since the turn-to-turn insulation is the Achilles heel for most of these motors, this will be the core subject in this dissertation. This problem has been an ordeal in the way of designers, due to its stochastic nature and the uncertainties associated with the different models proposed in the literature. With the development of this thesis, it is intended to model the phenomenon of partial discharges, combining finite element calculations with the results obtained in laboratory tests, to predict the appearance of partial discharges. Likewise, the impact of the different sources of uncertainty on the models will be analyzed. These uncertainties constitute a powerful tool for electrical designers, since they mark the strategy to follow in their design, according to the boundary conditions of the system.A finales del siglo XIX, los extraordinarios inventores y pioneros Nikola Tesla, Thomas Edison y George Westinghouse soñaron con transformar el mundo. Tras más de cien años desde entonces, la electricidad no ha dejado de crecer y se postula a convertirse en el mayor sistema industrial creado por la humanidad. La democratización de los coches híbridos y eléctricos, y aún más la futura electrificación de la industria aeronáutica son muestras de su imparable evolución. Como sistema en constante mejora y evolución, no ha estado exento de desafíos que superar sin comprometer su fiabilidad del mismo. Uno de los fenómenos que continúa siendo una amenaza y reduce la fiabilidad de las máquinas son las descargas parciales. Estos eventos afectan al sistema de aislamiento, pudiendo ocasionar un fallo del material que se puede traducir en daños de los equipos, interrupción del suministro eléctrico e incluso eventos incendiarios y explosivos. Una de las piedras angulares que las que se apoya este sistema eléctrico son los motores de corriente alterna. Espoleados por el progreso en los semiconductores y el descubrimiento del microprocesador, se han impuesto a los vetustos motores de corriente continua. Desde entonces, el control de electrónico de estos motores se han hecho imprescindible, hasta el punto de que para pequeñas potencias se vende un solo conjunto: “cobre, hierro y silicio”. De manera inesperada, este control mejorado de la velocidad causó una importante reducción de la fiabilidad de los motores, ocasionando fallos imprevistos en los sistemas de aislamiento. Puesto que el talón de Aquiles en la mayoría de estos motores es el aislamiento espira-espira, éste va a ser el objeto de estudio de estas tesis. Esta problemática ha sido un calvario en el camino de los diseñadores, debido a su carácter estocástico y las incertidumbres asociadas a los diferentes modelos propuestos en la literatura. Con el desarrollo de esta tesis, se pretende modelar el fenómeno de descargas parciales, combinando los cálculos de elementos finitos con los resultados obtenidos en los ensayos de laboratorio, para predecir la aparición de descargas parciales. Asimismo, se analizará el impacto que tienen en los modelos las diferentes fuentes de incertidumbre. Estas incertidumbres constituyen una potente herramienta para los diseñadores eléctricos, ya que les marcan la estrategia a seguir en su diseño, de acuerdo a las condiciones de contorno del sistema.Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de MadridPresidente: Armando Rodrigo Mor.- Secretario: Fernando Álvarez Gómez.- Vocal: Joaquín Granado Romer

Small-Scale Hydropower and Energy Recovery Interventions: Management, Optimization Processes and Hydraulic Machines Applications

Several topics in the small-scale hydropower sector are of great interest for pursuing the goal of a more sustainable relationship with the environment. The goal of this Special Issue entitled “Small-Scale Hydropower and Energy Recovery Interventions: Management, Optimization Processes and Hydraulic Machines Applications” was to collect the most important contributions from experts in this research field and to arouse interest in the scientific community towards a better understanding of what might be the main key aspects of the future hydropower sector. Indeed, the Guest Editors are confident that the Special Issue will have an important impact on the entire scientific community working in this research field that is currently facing important changes in paradigm to achieve the goal of net-zero emissions in both the energy and water sectors