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

Research and technology, 1993. Salute to Skylab and Spacelab: Two decades of discovery

A summary description of Skylab and Spacelab is presented. The section on Advanced Studies includes projects in space science, space systems, commercial use of space, and transportation systems. Within the Research Programs area, programs are listed under earth systems science, space physics, astrophysics, and microgravity science and applications. Technology Programs include avionics, materials and manufacturing processes, mission operations, propellant and fluid management, structures and dynamics, and systems analysis and integration. Technology transfer opportunities and success are briefly described. A glossary of abbreviations and acronyms is appended as is a list of contract personnel within the program areas

Advances in Rotating Electric Machines

It is difficult to imagine a modern society without rotating electric machines. Their use has been increasing not only in the traditional fields of application but also in more contemporary fields, including renewable energy conversion systems, electric aircraft, aerospace, electric vehicles, unmanned propulsion systems, robotics, etc. This has contributed to advances in the materials, design methodologies, modeling tools, and manufacturing processes of current electric machines, which are characterized by high compactness, low weight, high power density, high torque density, and high reliability. On the other hand, the growing use of electric machines and drives in more critical applications has pushed forward the research in the area of condition monitoring and fault tolerance, leading to the development of more reliable diagnostic techniques and more fault-tolerant machines. This book presents and disseminates the most recent advances related to the theory, design, modeling, application, control, and condition monitoring of all types of rotating electric machines

Yokeless radial electrodynamic bearing

When null-flux, passive electrodynamic bearings include a ferromagnetic yoke in front of the permanent magnets, the stiffness associated with the radial centering force becomes negative under a critical speed. This yields a strong instability and the necessity of using mechanical launch bearings at low speeds. In this paper, an electrodynamic bearing without ferromagnetic yoke is proposed. An analytical 2D model of the bearing is presented and some hypotheses are validated. The model is then used to perform a first analysis of the bearing performance. The force predictions correspond to expectations: the stiffness never reaches negative values. It is also shown that for given geometrical parameters, the performance of the studied bearing can be improved by choosing the appropriate number of phases and number of pole pairs of the winding

Yokeless radial electrodynamic bearing

Due to the presence of a ferromagnetic yoke in passive electrodynamic magnetic bearings, the stiffness associated with their radial centering force becomes negative under a critical speed. This leads to instability problems and to the necessity of using mechanical launch bearings at low speed. In this paper, an electrodynamic bearing without ferromagnetic yoke is proposed. An analytical 2D model of the bearing is presented and used to perform a first analysis of the bearing. The force predictions correspond to expectations: the stiffness never reaches negative values. It is also shown that for given geometrical dimensions, the performance of the studied bearing can be significantly improved by choosing the appropriate number of phases and number of pole pairs of the winding

Heteropolar null-flux electrodynamic bearings for the passive radial suspension of rotors

Magnetic bearings allow to support a rotating object without contact. This makes them more suitable than mechanical bearings for applications where removing the wear and/or the lubrication is highly sought-after, for example. Nowadays, the magnetic bearings used in the industry are controlled actively. This requires the use of sensors, controllers and power electronics. However, the complexity, cost and overall dimensions associated with this control system can become prohibitive, especially for small rated power applications. A way to overcome these disadvantages could be the use of magnetic bearings that do not require external control means, i.e. passive bearings. Electrodynamics bearings (EDBs) belong to this category. Electrodynamic bearings are based on the electromagnetic interaction forces between permanent magnets and currents flowing in a conductor. These currents are induced by the relative speed between the magnets and the conductors. For efficiency purposes, electrodynamic bearings are designed in such a way that there is no net variation in the permanent magnet flux linked by the winding when the rotor spins in a centered position. As a result, there are no induced currents, no forces, and above all no losses in the bearing when the rotor spins in a centered position. This characteristic is referred to as null-flux. It is found in all the designs of electrodynamic bearings that are studied nowadays. In contrast, when the rotor spins in an off-centered position, currents are induced in the winding. This creates a force on the rotor that tends to restore its centered position. In this case, the energy dissipated in the windings comes from the drive torque on the rotor that keeps the spin speed constant. On the one hand, this prevents the operation at zero spin speed. On the other hand, it eliminates the need for an additional electrical power supply to feed the bearing, as is the case for the existing active magnetic bearings. Finally, the absence of control system induces gains in compactness, simplicity, costs and reliability. As a result, electrodynamic bearings could be well suited for applications where these aspects are critical. Despite these advantages, electrodynamic bearings have not made their way out of the labs yet due to their lowstiffness and stability issues. In this context, this thesis aims at taking one further step toward the implementation of heteropolar electrodynamic bearings in practical applications. To this end, new design guidelines and models are proposed, validated, and applied to different case studies. Indeed, the design of a new electrodynamic bearing is usually based on the intuition and experience of its inventor. This work proposes guidelines to ease this design process. The guidelines are deduced by imposing the null-flux characteristic to a bearing comprising magnets with radial magnetic field and a winding with an arbitrary shape. This yields the identity q = p +/- 1, where q and p are the number of pole pairs of the winding and permanent magnets, respectively. Based on these guidelines, new bearing topologies are also introduced. Regarding the modeling, recent years have seen the emergence of a new kind of model of electrodynamic bearings. As opposed to the previous ones, this model is dynamic, i.e. obtained without making any assumption on the kinematics of the rotor axis. This opened the possibility of performing stability analyses in a rigorous way. Furthermore, the stability can be analyzed using conventional system analysis tools, because the model takes the form of a linear state-space representation. This thesis proposes a dynamic model with an enlarged scope, i.e. suitable for a wider range of bearing geometries. Thanks to this model, the performance and stability of various EDBs can be optimized and compared to find the most appropriate solution for a given application. Although various embodiments of heteropolar bearings have been proposed, very few efforts have been dedicated to the evaluation and optimization of their performance, and the actual potential of heteropolar EDBs still needs to be evaluated. In this aim, a graphical method based on the analysis of the root locus of the system is proposed. It is then applied to the comparison of bearings with different winding yoke permeabilities. Based on the dynamic model developed in this thesis, the optimization of the stability and stiffness of a yokeless bearing is also carried out, yielding a Pareto front of optimal bearings. These optimal bearings are finally compared to existing homopolar and heteropolar embodiments in terms of stiffness to magnet volume ratio, showing that similar ratios can be obtained. Lastly, the bearing dynamic model is applied to the prediction of balancing radial electrodynamic forces due to rotor eccentricities in permanent magnet machines. The main assumptions of the model are validated to show its applicability in this case, and the forces from the model are compared to finite element simulation results, showing a good agreement between both predictions.(FSA - Sciences de l'ingénieur) -- UCL, 201