Permanent Magnet Vernier Machine: A Review

Permanent magnet vernier machines (PMVMs) gained a lot of interest over the past couple of decades. This is mainly due to their high torque density enabled by the magnetic gearing effect. This study will provide a thorough review of recent advances in PMVMs. This review will cover the principle of operation and nature of magnetic gearing in PMVMs, and a better understanding of novel PMVM topologies using different winding configuration as well as different modulation poles and rotor structures. Detailed discussions on the choice of gear ratio, slot-pole combinations, design optimisation and role of advanced materials in PMVMs will be presented. This will provide an update on the current state-of-the art as well as future areas of research. Furthermore, the power factor issue, fault tolerance as well as cost reduction will be discussed highlighting the gap between the current state-of-the art and what is needed in practical applications

Magnetic Material Modelling of Electrical Machines

The need for electromechanical energy conversion that takes place in electric motors, generators, and actuators is an important aspect associated with current development. The efficiency and effectiveness of the conversion process depends on both the design of the devices and the materials used in those devices. In this context, this book addresses important aspects of electrical machines, namely their materials, design, and optimization. It is essential for the design process of electrical machines to be carried out through extensive numerical field computations. Thus, the reprint also focuses on the accuracy of these computations, as well as the quality of the material models that are adopted. Another aspect of interest is the modeling of properties such as hysteresis, alternating and rotating losses and demagnetization. In addition, the characterization of materials and their dependence on mechanical quantities such as stresses and temperature are also considered. The reprint also addresses another aspect that needs to be considered for the development of the optimal global system in some applications, which is the case of drives that are associated with electrical machines

Critical Aspects of Electric Motor Drive Controllers and Mitigation of Torque Ripple - Review

Electric vehicles (EVs) are playing a vital role in sustainable transportation. It is estimated that by 2030, Battery EVs will become mainstream for passenger car transportation. Even though EVs are gaining interest in sustainable transportation, the future of EV power transmission is facing vital concerns and open research challenges. Considering the case of torque ripple mitigation and improved reliability control techniques in motors, many motor drive control algorithms fail to provide efficient control. To efficiently address this issue, control techniques such as Field Orientation Control (FOC), Direct Torque Control (DTC), Model Predictive Control (MPC), Sliding Mode Control (SMC), and Intelligent Control (IC) techniques are used in the motor drive control algorithms. This literature survey exclusively compares the various advanced control techniques for conventionally used EV motors such as Permanent Magnet Synchronous Motor (PMSM), Brushless Direct Current Motor (BLDC), Switched Reluctance Motor (SRM), and Induction Motors (IM). Furthermore, this paper discusses the EV-motors history, types of EVmotors, EV-motor drives powertrain mathematical modelling, and design procedure of EV-motors. The hardware results have also been compared with different control techniques for BLDC and SRM hub motors. Future direction towards the design of EV by critical selection of motors and their control techniques to minimize the torque ripple and other research opportunities to enhance the performance of EVs are also presented.publishedVersio

Reliable Multiphase Induction Motor Drives

A motor is said to be reliable if it can run at its rated operating condition for a specified period of time. With the widespread use of electric motors in newer applications, reliability is a major concern in terms of safety as well as revenue. About 30-40% of reported failures in induction motors are due to stator faults. It is well known that a stator fault starts as an inter-turn fault within a phase and then propagates into phase-to-phase and phase-to-ground faults that can then lead to complete shutdown of the motor. Two approaches have been taken in this dissertation to make an induction motor drive system more tolerant to stator faults; integration of an inter-turn fault detection method into a five-phase induction motor drive and design of fault-tolerant induction motors. The phase redundancy of five-phase motors makes it possible to achieve continued operation of the motor with an open phase. However, for true fault tolerance the drive must be able to detect an incipient fault and then transition to post fault operation. A low-cost diagnostic method based on DC voltage injection has been developed for detection of inter-turn faults in five-phase induction motor drive systems. It has been shown that difference in DC current response to an injected voltage before and after an inter-turn fault serves as a reliable fault indicator. The diagnostic is non-intrusive, requires no additional hardware and effectively integrates both fault detection and fault-tolerant control into the motor controller. The method has been successfully implemented and tested on low-cost microcontroller. The propagation of a stator inter-turn fault into a phase-to-phase fault is worsened in distributed winding induction motors where the different phase windings overlap each other at the end connections. Tooth wound or fractional slot concentrated winding (FSCW) stators have non-overlapping end connections and hence more physical and thermal isolation between the phases as compared to distributed winding stators. While FSCW configurations have been widely used for permanent magnet motors, their adoption for induction motors is a challenge. An FSCW configuration has been designed for outer rotor induction motors by using a dual slot layer stator structure and multilayer windings. Comparison with a conventional induction motor shows an 11% reduction in the copper usage in addition to having non-overlapping phase windings

Electrical and magnetic faults diagnosis in permanent magnet synchronous motors

Permanent magnet synchronous motors (PMSMs) are an alternative in critical applications where high-speed operation, compactness and high efficiency are required. In these applications it is highly desired to dispose of an on-line, reliable and cost-effective fault diagnosis method. Fault prediction and diagnosis allows increasing electric machines performance and raising their lifespan, thus reducing maintenance costs, while ensuring optimum reliability, safe operation and timely maintenance. Consequently this thesis is dedicated to the diagnosis of magnetic and electrical faults in PMSMs. As a first step, the behavior of a healthy machine is studied, and with this aim a new 2D finite element method (FEM) modelbased system for analyzing surface-mounted PSMSs with skewed rotor magnets is proposed. It is based on generating a geometric equivalent non-skewed permanent magnet distribution which accounts for the skewed distribution of the practical rotor, thus avoiding 3D geometries and greatly reducing the computational burden of the problem. To diagnose demagnetization faults, this thesis proposes an on-line methodology based on monitoring the zero-sequence voltage component (ZSVC). Attributes of the proposed method include simplicity, very low computational burden and high sensibility when compared with the well known stator currents analysis method. A simple expression of the ZSVC is deduced, which can be used as a fault indicator parameter. Furthermore, mechanical effects arising from demagnetization faults are studied. These effects are analyzed by means of FEM simulations and experimental tests based on direct measurements of the shaft trajectory through self-mixing interferometry. For that purpose two perpendicular laser diodes are used to measure displacements in both X and Y axes. Laser measurements proved that demagnetization faults may induce a quantifiable deviation of the rotor trajectory. In the case of electrical faults, this thesis studies the effects of resistive unbalance and stator winding inter-turn short-circuits in PMSMs and compares two methods for detecting and discriminating both faults. These methods are based on monitoring and analyzing the third harmonic component of the stator currents and the first harmonic of the ZSVC. Finally, the Vold-Kalman filtering order tracking algorithm is introduced and applied to extract selected harmonics related to magnetic and electrical faults when the machine operates under variable speed and different load levels. Furthermore, different fault indicators are proposed and their behavior is validated by means of experimental data. Both simulation and experimental results show the potential of the proposed methods to provide helpful and reliable data to carry out a simultaneous diagnosis of resistive unbalance and stator winding inter-turn faults

Optimal Design of Modular High Performance Brushless Wound Rotor Synchronous Machine for embedded systems

This thesis is dedicated to the design and the optimization of modular brushless wound rotor synchronous machine for embedded systems. This machine is constructed based on POKIPOKITM structure with integrated drive electronics. Finite element analysis based optimization becomes more popular in the field of electrical machine design because analytical equations are not easily formalized for the machines which have complicate structures. Using electromagnetic analysis to comparatively study different modular brushless wound rotor synchronous machines and therefore, to select the structure which offers the best fault tolerant capability and the highest output performances. Firstly, the fundamental winding factor calculated by using the method based on voltage phasors is considered as a significant criterion in order to select the numbers of phases, stator slots and poles. After that, 2D finite element numerical simulations are carried out for a set of 15 machines to analyze their performances. The simulation results are then compared to find an appropriate machine according to torque density, torque ripple and machine efficiency. The 7phase/7-slot/6-pole machine is chosen and compared with a reference design surfacemounted permanent magnet synchronous machine in order to evaluate the interesting performance features of the wound rotor synchronous machine. In the second design stage, this machine is optimized by using derivative-free optimization. The objective is to minimize external volume under electromagnetic, thermal and mechanical constraints. Given that an accurate finite element analysis for machine performance takes a long time. Moreover, considering that the average torque can be obtained by simulating the model with only four rotor positions instead of one electric period, optimization strategy is proposed to reduce computational time and therefore, obtain a fast convergence ability by defining relaxed problems which enable minimizing the external volume of the machine under only several constraints such as average torque, torque ripple and copper losses. By testing relaxed problems, two different optimization methods (NOMAD and fmincon) are compared in order to select an appropriate method for our optimization problem. Using NOMAD method based on Mesh Adaptive Direct Search, we achieve optimal results which satisfy all of the constraints proposed. In the third design stage, all constraints are validated by 3D electromagnetic and thermal simulations using finite element and computational fluid dynamics methods. The 3D results show that the average torque obtained is lower than the desired value. By increasing the length of the machine, a new corrected machine is thus obtained. It can be observed that the iron losses obtained in 3D are higher than that in 2D due to the leakage flux in the end-winding. Then, the machine temperature is analyzed by using ANSYS Fluent. Note that the surface temperature is higher than that calculated in the optimization and the coil temperature is 8.48°C higher than the desired value (105°C). However, some dissipation by the shaft and the bearings of the machine are expected to reduce the machine temperature. Finally, a machine prototype is built and some experimental tests are carried out. The results show that the electromotive force has a similar waveform compared to 3D prediction and the difference of the measured and predicted maximum static torques is small

Fractional slot concentrated winding PM synchronous motors for transport electrification applications

Moving towards electrification of transport including electric vehicles (EV), more electric aircraft (MEA), and electric ships offers a crucial way in dealing with global carbon emissions and climate change. Electric motors are a key enabling technique in these applications, but their increased use is associated with requirements of extreme power/torque density, excellent fault-tolerance, high efficiency, and good manufacturability. The main goal of this thesis is to study permanent magnet electric machine winding theory to determine the suitable electric machine winding topologies for different applications. Two separate vehicle transport applications are investigated, including an EV traction motor and a novel modular electromechanical actuator (EMA) for MEA. The study of the EV traction motor involves the investigation of methods for reducing the significant stator MMF harmonics in fractional slot concentrated winding (FSCW) electric machines, and the development of novel FSCW topologies while keeping the benefits of easy manufacturing and the non-overlapping characteristic of concentrated windings. The novel FSCW topologies can be extended to multi-phase FSCW motors. A traction motor equipped with a novel 24 slots, 14 poles FSCW topology and interior PM (IPM) rotor is developed for evaluation. The performance under normal and fault conditions is fully explored and validated with simulation and experimental results, which demonstrates the applicability and strong potential of the proposed 24 slots, 14 poles IPM motor in fault-tolerant traction motor applications. The second topic focuses on modular fault-tolerant EMAs for aircraft actuation systems which can meet a diverse range of requirements. The architecture and design considerations of the actuator system are firstly determined considering reliability, fault-tolerance, and weight. The modular EMA scheme consisting of a direct-drive rotary motor and mechanical screw is identified. A dual 3-phase 24 slots, 22 poles FSCW motor with a surface-mounted permanent magnet (SPM) rotor is developed and evaluated in terms of electromagnetics, thermal management, and fault-tolerance. Experimental results of the modular EMA motor prototypes agree well with predicted results. All this confirms the applicability and satisfactory implementation of the modular EMA motor for aircraft actuation system applications

Permanent magnet Vernier machines for direct-drive offshore wind power: benefits and challenges

Permanent magnet Vernier (PM-V) machines, at low power levels (few kWs), have shown a great potential to improve the torque density of existing direct-drive PM machines without much compromising on efficiency or making the machine structure more complicated. An improved torque density is very desirable for offshore wind power applications where the size of the direct-drive machine is an increasing concern. However, the relatively poor power factors of the PM-V machines will increase the power converter rating and hence cost. The objective of this paper is to review the benefits and challenges of PM-V machines for direct-drive offshore wind power applications. The review has been presented considering the system-level (direct-drive generator + converter) performance comparison between the surface-mounted permanent magnet Vernier (SPM-V) machines and the conventional SPM machines. It includes the indepth discussion on the challenges facing the PM-V machines when they are scaled up for multi-MW offshore wind power application. Other PM-V topologies discussed in literature have also been reviewed to asses their suitability for offshore wind power application

BADANIE WPŁYWU UŁAMKOWEJ LICZBY SZCZELIN BIEGUNÓW NA GENERACJĘ TURBINY WIATROWEJ PRZY UŻYCIU ULEPSZONEGO ALGORYTMU OPTYMALIZACJI CĘTKOWANEJ HIENY

The design of machines with permanent magnets is actively developing day by day and is often used in wind energy. The main advantages of such variable speed drives are high efficiency, high power density and torque density. When designing a wind generator with two rotors and permanent magnets, it is necessary to solve such a problem as the correct choice of the number of poles and slots to increase efficiency and minimize the cost of the machine. In this work, an improved spotted hyena optimization algorithm is used to obtain the optimal combination of slots and poles. This optimization algorithm makes it possible to obtain the number of fractional slots per pole and evaluate the operating efficiency of a wind generator with a double rotor and ferrite magnets. At the first stage of machine design, various combinations of slots are installed. Next, the optimal combination is selected from various slot-pole combinations, taking into account the Enhanced Spotted Hyena Optimization (ESHO) algorithm, in which a multi-objective function is configured. Accordingly, the multi-objectives are the integration of reverse electromotive force, output torque, gear torque, flux linkage, torque ripple along with losses. Analysis of the results obtained shows that the proposed algorithm for determining the optimal slot combination is more efficient than other slot combinations. It has also been found that the choice of slot and pole combination is critical to the efficient operation of permanent magnet machines.Projektowanie maszyn z magnesami trwałymi aktywnie rozwija się z dnia na dzień i jest często wykorzystywane w energetyce wiatrowej. Głównymi zaletami takich napędów o zmiennej prędkości są wysoka sprawność, wysoka gęstość mocy i gęstość momentu obrotowego. Podczas projektowania generatora wiatrowego z dwoma wirnikami i magnesami trwałymi konieczne jest rozwiązanie takiego problemu, jak prawidłowy dobór liczby biegunów i szczelin w celu zwiększenia wydajności i zminimalizowania kosztów maszyny. W niniejszej pracy zastosowano ulepszony algorytm optymalizacji hieny plamistej w celu uzyskania optymalnej kombinacji szczelin i biegunów. Ten algorytm optymalizacji umożliwia uzyskanie liczby ułamkowych szczelin na biegun i ocenę wydajności operacyjnej generatora wiatrowego z podwójnym wirnikiem i magnesami ferrytowymi. Na pierwszym etapie projektowania maszyny instalowane są różne kombinacje szczelin. Następnie wybierana jest optymalna kombinacja spośród różnych kombinacji szczelin i biegunów, biorąc pod uwagę algorytm Enhanced Spotted Hyena Optimization (ESHO) (ulepszony algorytm optymalizacjihieny cętkowanej hieny), w którym skonfigurowana jest funkcja wielocelowa. W związku z tym, celami wielozadaniowymi są integracja odwrotnej siły elektromotorycznej, wyjściowego momentu obrotowego, momentu obrotowego przekładni, połączenia strumienia, tętnienia momentu obrotowego wraz ze stratami. Analiza uzyskanych wyników pokazuje, że proponowany algorytm określania optymalnej kombinacji szczelin jest bardziej wydajny niż inne kombinacje szczelin. Stwierdzono również, że wybór kombinacji szczelin i biegunów ma kluczowe znaczenie dla wydajnej pracy maszyn z magnesami trwałymi

Fractional slot concentrated winding PM synchronous motors for transport electrification applications

Moving towards electrification of transport including electric vehicles (EV), more electric aircraft (MEA), and electric ships offers a crucial way in dealing with global carbon emissions and climate change. Electric motors are a key enabling technique in these applications, but their increased use is associated with requirements of extreme power/torque density, excellent fault-tolerance, high efficiency, and good manufacturability. The main goal of this thesis is to study permanent magnet electric machine winding theory to determine the suitable electric machine winding topologies for different applications. Two separate vehicle transport applications are investigated, including an EV traction motor and a novel modular electromechanical actuator (EMA) for MEA. The study of the EV traction motor involves the investigation of methods for reducing the significant stator MMF harmonics in fractional slot concentrated winding (FSCW) electric machines, and the development of novel FSCW topologies while keeping the benefits of easy manufacturing and the non-overlapping characteristic of concentrated windings. The novel FSCW topologies can be extended to multi-phase FSCW motors. A traction motor equipped with a novel 24 slots, 14 poles FSCW topology and interior PM (IPM) rotor is developed for evaluation. The performance under normal and fault conditions is fully explored and validated with simulation and experimental results, which demonstrates the applicability and strong potential of the proposed 24 slots, 14 poles IPM motor in fault-tolerant traction motor applications. The second topic focuses on modular fault-tolerant EMAs for aircraft actuation systems which can meet a diverse range of requirements. The architecture and design considerations of the actuator system are firstly determined considering reliability, fault-tolerance, and weight. The modular EMA scheme consisting of a direct-drive rotary motor and mechanical screw is identified. A dual 3-phase 24 slots, 22 poles FSCW motor with a surface-mounted permanent magnet (SPM) rotor is developed and evaluated in terms of electromagnetics, thermal management, and fault-tolerance. Experimental results of the modular EMA motor prototypes agree well with predicted results. All this confirms the applicability and satisfactory implementation of the modular EMA motor for aircraft actuation system applications