Synchronous reluctance generator with ferrite magnets for wind turbine

Synchronous reluctance generators with ferrite magnets in the rotor (PMSynRG) are a good alternative to synchronous generators (SG) with rare-earth magnets. The comparison between a SG with rare-earth magnets and a PMSynRG with ferrite magnets of the same diameter, stack length, power and speed is given in the paper. Twice as less magnets are required for the PMSynRG with ferrite magnets than for the SG with rare-earth magnets. The cost of the ferrite magnets is 4.4 times less than of the rare earth magnets. Also, the PMSynRG with ferrite magnets has much higher efficiency than the SG. The half-integer slot number per pole and phase is chosen to achieve rather low torque ripple without skewing the rotor. © 2018 Institute of Physics Publishing.All Rights Reserved

High efficiency sensorless fault tolerant control of permanent magnet assisted synchronous reluctance motor

In the last decades, the development trends of high efficiency and compact electric drives on the motor side focused on Permanent Magnet Synchronous Machines (PMSMs) equipped with magnets based on the rare-earth elements. The permanent magnet components, however, dramatically impact the overall bill of materials of motor construction. This aspect has become even more critical due to the price instability of the rare-earth elements. This is why the Permanent Magnet Assisted Synchronous Reluctance Motor (PMaSynRM) concept was brought to the spotlight as it gives comparable torque density and similar efficiencies as PMSM although at a lower price accredited for the use of magnets built with ferrite composites. Despite these advantages, PMaSynRM drive design is much more challenging because of nonlinear inductances resulting from deep cross saturation effects. It is also true for multi-phase PMSM motors that have gained a lot of attention as they proportionally split power by the increased number of phases. Furthermore, they offer fault-tolerant operation while one or more phases are down due to machine, inverter, or sensor fault. The number of phases further increases the overall complexity for modeling and control design. It is clear then that a combination of multi-phase with PMaSynRM concept brings potential benefits but confronts standard modeling methods and drive development techniques. This Thesis consists of detailed modeling, control design, and implementation of a five-phase PMaSynRM drive for normal healthy and open phase fault-tolerant applications. Special emphasis is put on motor modeling that comprises saturation and space harmonics together with axial asymmetry introduced by rotor skewing. Control strategies focused on high efficiency are developed and the position estimation based on the observer technique is derived. The proposed models are validated through Finite Element Analysis (FEA) and experimental campaign. The results show the effectiveness of the elaborated algorithms and methods that are viable for further industrialization in PMaSynRM drives with fault-tolerant capabilities.En últimas décadas, las tendencias de desarrollo de accionamientos eléctricos compactos y de alta eficiencia en el lado del motor se centraron en las maquinas síncronas de imanes permanentes (PMSM) equipadas con imanes basados en elementos de tierras raras. Sin embargo, los componentes de imán permanente impactan dramáticamente en el coste de construcción del motor. Este aspecto se ha vuelto aún más crítico debido a la inestabilidad de precios de los elementos de tierras raras. Esta es la razón por la que el concepto de motor de reluctancia síncrona asistido por imán permanente (PMaSynRM) se ha tomado en consideración, ya que ofrece una densidad de par comparable y eficiencias similares a las de PMSM, aunque a un precio más bajo acreditado para el uso de imanes construidos con compuestos de ferritas. A pesar de drive PMaSynRM resulta muy complejo debido a las inductancias no lineales que resultan de los efectos de saturación cruzada profunda. Esto también es cierto para los motores PMSM polifásicos que han ganado mucha atención en los últimos años, en los que se divide proporcionalmente la potencia por el mayor número de fases. Además, ofrecen operación tolerante a fallas mientras una o más fases están inactivas debido a fallas en la máquina, el inversor o el sensor. Sin embargo, el número de fases aumenta aún más la complejidad general del diseño de modelado y control. Está claro entonces que una combinación de multifase con el concepto PMaSynRM tiene beneficios potenciales, pero dificulta los métodos de modelado estándar y las técnicas de desarrollo del sistema de accionamiento. Esta tesis consiste en el modelado detallado, el diseño de control y la implementación de un drive PMaSynRM de cinco fases para aplicaciones normales en buen estado y tolerantes a fallas de fase abierta. Se pone especial énfasis en el modelado del motor que comprende la saturación y los armónicos espaciales junto con la asimetría axial introducida por la inclinación del rotor. Se desarrollan estrategias de control enfocadas a la alta eficiencia y se deriva la estimación de posición basada en la técnica del observador. Los modelos propuestos se validan mediante Análisis de Elementos Finitos (FEA) y resultados experimentales. Los resultados muestran la efectividad de los algoritmos y métodos elaborados, que resultan viables para la industrialización de unidades PMaSynRM con capacidades tolerantes a fallas.Postprint (published version

Analysis and implementation of a methodology for optimal PMa-SynRM design taking into account performances and reliability

Automotive applications focus to develop drive-train technologies with higher energy efficiency and lower environmental impact. Electric and hybrid vehicles are gaining popularity since they fulfill these requirements . The aim of optimal motor design is to achieve high torque and power densities, wider speed range and high efficiency within the area defining the most frequent operating points. This work presents a methodology to optimize electric motors for traction applications considering a multi-physics approach. The magnetic behavior is evaluated using a complex reluctance networks capable to compute the cross-coupling. The results of the magnetic model are the inductances, iron losses, and magnet flux linkage. The thermal behavior is evaluated using a thermal network and it is coupled with the magnetic model. The electric model is feed with the solution of the thermal and magnetic model. The electric model aims to calculate the whole operating area of the motor to allow optimizing the machine considering the most frequent operating zone. Therefore, a fast tool to evaluate different variables within the torque-speed map is convenient for this purpose. In this context, starting from a preliminary motor design, and taking into account motor cross-coupling effects and power losses, this thesis presents a new methodology for optimizing and evaluating the behavior of permanent magnet machines, such as synchronous reluctance machines, and permanent magnet assisted synchronous reluctance machines, in all operational points. Apart from the torque and efficiency, many other electrical variables can be obtained, such as the current space vector angle, power factor or electrical power among others. The proposed methodology also allows optimizing the design of the machine under a pre­established control law; thus obtaining the current set point trajectory in the dq frame and allowing a fast and accurate evaluation of motor performance.The results obtained by means of the proposed simulation tool are compared against finite element analysis simulations and experimental data, thus validating the usefulness and accuracy of the proposed methodology.El sector de la automoción se está centrando en las tecnologías con alta eficiencia y un bajo impacto medioambiental. En este sentido el desarrollo de vehiculos eléctricos o hibridos está ganando importancia en este sector. Por lo tanto, el diseño de motores eléctricos que cumplan las especificaciones necesarias para aplicaciones de tracción eléctrica es un punto de especial interés . El principal objetivo en la optimización de motores eléctricos es conseguir altas densidades de par o potencia, alta eficiencia y un buen factor de potencia, teniendo en cuenta la zona de trabajo más común. Este trabajo presenta una metodologia para optimización de motores eléctricos, concretamente motores de reluctancia síncrona, para aplicaciones de tracción eléctrica. Para ello es necesario crear diferentes modelos para evaluar el comportamiento eléctrico, térmico y magnético del motor así como calcular los diferentes puntos de trabajo. El modelo magnético, que está basado en redes de reluctancia, permite calcular las inductancias, el flujo magnético del imán y las pérdidas en el hierro teniendo en cuenta la saturación cruzada. El modelo térmico estará basado en redes térmicas y permite evaluar la temperatura de diferentes partes del motor (dientes, bobinado, cabezas de bobina o imanes) para evaluar la viabilidad de estos motores y definir bien el valor de algunos parámetros como la resistencia del bobinado y las propiedades magnéticas del imán. El modelo eléctrico está basado en la resolución de las ecuaciones completas del motor en los ejes dq, los parámetros necesarios (inductancias, resistencia, perdidas en el hierro, flujo del imán) serán obtenidos en los modelos magnético y térmico. En este punto, la metodología propuesta es capaz de calcular todos los puntos de operación de la máquina. Hay que remarcar que en este punto se puede calcular la eficiencia, factor de potencia, ángulo de corriente. La tesis propuesta empezará el proceso diseño optimizado del motor calculando un pre-diseño para introducirlo en un optimizador que usará los mapas calculados para evaluar su función de coste teniendo en cuenta que estos mapas estarán obtenidos considerando saturación cruzada, perdidas en el hierro y variaciones de temperatura, se puede afirmar que el motor resultante está evaluado en todos sus dominios exceptuando el mecánico. Para el análisis mecánico se propone un estudio en elementos finitos posterior a la optimización. En este análisis se podrán introducir estructuras que mejoren la resistencia mecánica del motor y que serán restricciones para una nueva optimización. Una vez cerrado el proceso iterativo entre optimización y análisis mecánico se tendria el motor final. En la tesis propuesta se usa esta metodologia para diseñar varios motores, con lo cual se permite la validación de la misma.Postprint (published version

Design optimization and performance analysis methodology for PMSMs to improve efficiency in hydraulic applications

Pla de Doctorats Industrials de la Generalitat de CatalunyaIn the recent years, water pumping and other hydraulic applications are increasingly demanding motors capable to operate under different working conditions, including variable pressure and volumetric flow demands. Moreover, the technical evolution trend of pumping components is to minimize the size, offering compact and adaptable hydraulic units. Hence, the need to optimize the electric motor part to reduce the volume according this trend, maximizing the efficiency, decreasing material and fabrication costs, reducing noise and improving thermal dissipation have originated the research field of this project. So far different methodologies have been focused on designing electrical machines considering few aspects, such as the rated conditions with some size limitations. In addition, the optimization strategies have been based on single operation conditions, improving multiple aspects but not considering the overall performance of the machine and its influence with the working system. This research changes the design and optimization paradigm, focusing on defining beforehand the desired performance of the electrical machine in relation with the application system. The customization is not limited to an operating point but to the whole performance space, which in this case is the torque-speed area. Thus, the designer has plenty of freedom to study the system, and define the desired motor performance establishing the size, thermal and mechanical limitations from the beginning of the process. Moreover, when designing and optimizing electrical machines, the experimental validation is of major importance. From an industrial scope so far, the testing methodologies are focused on evaluating point by point the electrical machine performance, being a robust and trustable way to measure and validate the electrical machine characteristics. Nevertheless,this method requires a large time to prepare the experimental setup and to evaluate the whole motor performance. For this reason, there is a special interest on improving parameter estimation and performance evaluation techniques for electrical machines to reduce evaluation time, setup complexity and increase the number of physical magnitudes to measure in order to have deeper information. This research also develops methodologies to extend the electrical machine experimental validation providing information to evaluate the motor performance. This doctoral thesis has been developed with a collaboration agreement between UPC and the company MIDTAL TALENTOS S.L. The thesis is included within the Industrial Doctorates program 2018 DI 019 promoted by the Generalitat de Catalunya.En los últimos años, el bombeo de agua, entre otras aplicaciones hidráulicas, exige cada vez más motores capaces de operar en diferentes condiciones de trabajo, incluyendo las demandas variables de presión y caudal volumétrico. Además, la evolución técnica de los componentes de bombeo está cada vez más minimizando el tamaño ofreciendo unidades hidráulicas compactas y adaptables. De ahí la necesidad de optimizar la parte del motor eléctrico para reducir el volumen de acuerdo con esta tendencia, maximizando la eficiencia, disminuyendo los costos de material y fabricación, reduciendo el ruido y mejorando la disipación térmica. Todos estos factores han creado el campo de investigación sobre el cual se desarrolla este proyecto. Hasta ahora las metodologías se han centrado en diseñar las máquinas eléctricas considerando unos pocos aspectos técnicos, como las condiciones nominales con algunas limitaciones de tamaño. Además, las estrategias de optimización se han basado en condiciones de operación única, mejorando múltiples aspectos sin considerar el rendimiento general de la máquina y su influencia en el sistema de trabajo. Esta investigación cambia el paradigma de diseño y optimización centrándose en definir de antemano el rendimiento deseado de la máquina eléctrica en relación con el sistema de aplicación. La personalización no se limita a un punto de funcionamiento sino a todo el espacio de operación, que en este caso se expresa en el espacio par-velocidad. Así, el diseñador tiene libertad para estudiar el sistema, definir el rendimiento deseado del motor estableciendo el tamaño, limitaciones térmicas y mecánicas desde el inicio del proceso. Además, a la hora de diseñar y optimizar máquinas eléctricas, la validación experimental es de gran importancia. En el ámbito industrial hasta ahora, las metodologías de ensayo han sido enfocadas a evaluar punto por punto la máquina eléctrica, siendo una forma robusta y confiable de medir y validar sus características. Sin embargo, este método requiere mucho tiempo para preparar la configuración experimental y evaluar el motor en toda su zona de operación. Por esta razón, existe un interés especial en mejorar la estimación de parámetros y las técnicas de evaluación de la operación de las máquinas eléctricas reduciendo tiempo, complejidad y aumentando el número de magnitudes físicas a medir teniendo más información sobre la máquina. Esta investigación también desarrolla metodologías para extender la validación experimental de la máquina eléctrica proporcionando información para evaluar el rendimiento del motor. Esta tesis doctoral ha sido desarrollada con un convenio de colaboración entre la Universidad Politécnica de Cataluña UPC y la empresa MIDTAL TALENTOS S.L. La tesis se engloba dentro del plan de Doctorados Industriales 2018 DI 019 impulsado por la Generalitat de Catalunya.Postprint (published version

High-speed electrical machines: technologies, trends and developments

This paper reviews the current technologies used in high speed electrical machines, through an extensive survey of different topologies developed and built in industry as well as in academia for several applications. Developments in materials and components including electrical steels and copper alloys are discussed, and their impact on the machines’ operating physical boundaries is investigated. The main application areas pulling the development of high speed machines are also reviewed in an effort to better understand the typical performance requirements

Investigation of novel multi-layer spoke-type ferrite interior permanent magnet machines

The permanent magnet synchronous machines have been attracting more and more attention due to the advantages of high torque density, outstanding efficiency and maturing technologies. Under the urges of mandatory energy efficiency requirements, they are considered as the most potential candidates to replace the comparatively low-efficient induction machines which dominate the industrial market. However, most of the high performance permanent magnet machines are based on high cost rare-earth materials. Thus, there will be huge demands for low-cost high-performance permanent magnet machines. Ferrite magnet is inexpensive and abundant in supply, and is considered as the most promising alternative to achieve the goal of low cost and high performance. In consideration of the low magnetic energy, this thesis explored the recent developments and possible ideas of ferrite machines, and proposed a novel multi-layer spoke-type interior permanent magnet configuration combining the advantages of flux focusing technique and multi-layer structure. With comparable material cost to induction machines, the proposed ferrite magnet design could deliver 27% higher power with 2-4% higher efficiency with exactly the same frame size. Based on the data base of International Energy Agency (IEA), electricity consumed by electric machines reached 7.1PWh in 2006 [1]. Considering that induction machines take up 90% of the overall industrial installation, the potential energy savings is enormous. This thesis contributes in five key aspects towards the investigation and design of low-cost high-performance ferrite permanent magnet machines. Firstly, accurate analytical models for the multi-layer configurations were developed with the consideration of spatial harmonics, and provided effective yet simple way for preliminary design. Secondly, the influence of key design parameters on performance of the multi-layer ferrite machines were comprehensively investigated, and optimal design could be carried out based on the insightful knowledge revealed. Thirdly, systematic investigation of the demagnetization mechanism was carried out, focusing on the three key factors: armature MMF, intrinsic coercivity and working temperature. Anti-demagnetization designs were presented accordingly to reduce the risk of performance degradation and guarantee the safe operation under various loading conditions. Then, comparative study was carried out with a commercial induction machine for verification of the superior performance of the proposed ferrite machine. Without loss of generality, the two machines had identical stator cores, same rotor diameter and stacking length. Under the operating condition of same stator copper loss, the results confirmed the superior performance of the ferrite machine in terms of torque density, power factor and efficiency. Lastly, mechanical design was discussed to reduce the cost of mass production, and the experimental effort on the prototype machine validates the advantageous performance as well as the analytical and FEA predictions

Design Simulation and Experiments on Electrical Machines for Integrated Starter-Generator Applications

This thesis presents two different non-permanent magnet machine designs for belt-driven integrated starter-generator (B-ISG) applications. The goal of this project is to improve the machine performance over a benchmark classical switched reluctance machine (SRM) in terms of efficiency, control complexity, torque ripple level and power factor. The cost penalty due to the necessity of a specially designed H-bridge machine inverter is also taken into consideration by implementation of a conventional AC inverter. The first design changes the classical SRM winding configuration to utilise both self-inductance and mutual-inductance in torque production. This allows the use of AC sinusoidal current with lower cost and comparable or even increased torque density. Torque density can be further increased by using a bipolar square current drive with optimum conduction angle. A reduction in control difficulty is also achieved by adoption of standard AC machine control theory. Despite these merits, the inherently low power factor and poor field weakening capability makes these machines unfavourable in B-ISG applications. The second design is a wound rotor synchronous machine (WRSM). From FE analysis, a six pole geometry presents a lower loss level over four pole geometry. Torque ripple and iron loss are effectively reduced by the use of an eccentric rotor pole. To determine the minimum copper loss criteria, a novel algorithm is proposed over the conventional Lagrange method, where the deviation is lowered from ± 10% to ± 1%, and the simulation time is reduced from hours to minutes on standard desktop PC hardware. With the proposed design and control strategies, the WRSM delivers a comparable field weakening capability and a higher efficiency compared with the benchmark SRM under the New European Driving Cycle, where a reduction in machine losses of 40% is possible. Nevertheless, the wound rotor structure brings mechanical and thermal challenges. A speed limit of 11,000 rpm is imposed by centrifugal forces. A maximum continuous motoring power of 3.8 kW is imposed by rotor coil temperature performance, which is extended to 5 kW by a proposed temperature balancing method. A prototype machine is then constructed, where the minimum copper loss criteria is experimentally validated. A discrepancy of no more than 10% is shown in back-EMF, phase voltage, average torque and loss from FE simulation

Some aspects of high-torque, low-speed, brushless electric motors

Imperial Users onl

Design Optimization of Permanent Magnet Machines Over a Target Operating Cycle Using Computationally Efficient Techniques

The common practices of large-scale finite element (FE) model-based design optimization of permanent magnet synchronous machines (PMSMs) oftentimes aim at improving the machine performance at the rated operating conditions, thus overlooking the performance treatment over the entire range of operation in the constant torque and extended speed regions. This is mainly due to the computational complexities associated with several aspects of such large-scale design optimization problems, including the FE-based modeling techniques, large number of load operating points for load-cycle evaluation of the design candidates, and large number of function evaluations required for identification of the globally optimal design solutions. In this dissertation, the necessity of accommodating the entire range of operation in the design optimization of PMSMs is demonstrated through joint application of numerical techniques and mathematical or statistical analyses. For this purpose, concepts such as FE analysis (FEA), design of experiments (DOE), sensitivity analysis, response surface methodology (RSM), and regression analysis are extensively used throughout this work to unscramble the correlations between various factors influencing the design of PMSMs. Also in this dissertation, computationally efficient methodologies are developed and employed to render unprohibitive the problems associated with large-scale design optimization of PMSMs over the entire range of operation of such machines. These include upgrading an existing computationally efficient FEA to solve the electromagnetic field problem at any load operating point residing anywhere in the torque-speed plane, developing a new stochastic search algorithm for effectively handling the constrained optimization problem (COP) of design of electric machines so as to reduce the number of function evaluations required for identifying the global optimum, implementing a k-means clustering algorithm for efficient modeling of the motor load profile, and devising alternative computationally efficient techniques for calculation of strand eddy current losses or characterization of the mechanical stress due to the centrifugal forces on the rotor bridges. The developed methodologies in this dissertation are applicable to the wide class of sine-wave driven PM and synchronous reluctance machines. Here, they were successfully utilized for optimization of two existing propulsion traction motors over predefined operating cycles. Particularly, the well-established benchmark design provided by the Toyota Prius Gen. 2 V-type interior PM (IPM) motor, and a challenging high power density spoke-type IPM for a formula E racing car are treated