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Introduction. The active and reactive (inductive) winding resistances of three-phase asynchronous motors (IM) are investigated. These important parameters are determined during design and are the basis for calculating a number of energy parameters and characteristics. Problem. In the classical design of IM, the winding resistances are determined with insufficient accuracy due to a number of assumptions and conventions. Especially it concerns the operation of IM with increased slip and it affects the accuracy of realization of its design data, starting parameters and characteristics. Goal. The paper aims to further develop the IM design system by numerical-field computational analysis of active and reactive resistances of the IM windings in the whole range of changes in its slip and calculation of the mechanical characteristic of IM to confirm the adequacy of the calculations of these resistances. Methodology. Resistances of the IM windings are determined by numerous calculations of the magnetic fields of dispersion with the FEMM program within stator and rotor teeth steps, and with current displacement in a squirrel-cage rotor core. Everything is done in the slip range when operating from start-up to idle with changing currents in the slots and the corresponding magnetic saturation of the core teeth. A Lua script has been created for the calculations, controlling the FEMM program and providing automation of all calculations. Results. The numerical-field method shows that the classical design method gives very large errors in determining the magnetic conductivities of IM slot dispersion, as well as current displacement in the bars of the squirrel-cage rotor winding. This is especially evident with increased slips in the start-up mode. Originality. Numerical estimates of the differences between the classical and numerical-field methods are given and the origin of errors is analyzed: the strong saturation of the teeth of the stator and rotor cores. This leads to a significant decrease in the magnetic conductivities of slot dispersion and the practical absence of current displacement in the rotor bars, on which the main emphasis was previously made. The obtained results made it possible to calculate the mechanical characteristic of the IM according to a transparent formula without the use of correction coefficients and reference graphical functions. Practical value. The provided technique of numerical-field analysis and the obtained results of the calculation of active and reactive winding resistances and mechanical characteristic are recommended as a basis for the improvement of the IM design system., Досліджуються реактивні (індуктивні) опори розсіяння і активні опори обмоток трифазних асинхронних двигунів (ТАД). Ці їхні важливі параметри визначаються при проєктуванні і є основою для розрахунку низки енергетичних параметрів та характеристик. При класичному проєктуванні ТАД опори обмоток визначаються з недостатньою точністю через низку припущень і умовностей. Особливо це стосується роботи ТАД з підвищеним ковзанням і відбивається на точності реалізації його проєктних даних, пускових параметрів та характеристик. Метою роботи є подальший розвиток системи проєктування ТАД шляхом чисельно-польового розрахункового аналізу активних і реактивних опорів обмоток ТАД у всьому діапазоні зміни його ковзання, і розрахунок механічної характеристики ТАД для підтвердження адекватності розрахунків цих опорів. Опори обмоток ТАД визначаються чисельними розрахунками магнітних полів розсіяння програмою FEMM у межах зубцевих кроків статора і ротора, а в стрижні короткозамкненого ротора – з витісненням струму. Все робиться у діапазоні ковзання при роботі від пуску до неробочого ходу зі зміною струмів в пазах і відповідного магнітного насичення зубців осердь. Для розрахунків створено скріпт Lua, який керує програмою FEMM і забезпечує автоматизацію усіх обчислень. Чисельно-польовим методом показано, що класична методика проєктування дає дуже великі похибки у визначенні магнітних провідностей пазового розсіяння ТАД, а також витіснення струму в стрижнях короткозамкненої обмотки ротора. Особливо це проявляється при підвищених ковзаннях у пусковому режимі. Надано числові оцінки розходжень класичного і чисельно-польового методів і проаналізовано походження похибок – сильне насичення зубців осердь статора і ротора. Це призводить до значного зменшення магнітних провідностей пазового розсіяння і практичної відсутності витіснення струму в стрижнях ротора, на яке раніше робився основний акцент. Отримані результати дозволили розрахувати механічну характеристику ТАД за прозорою формулою без використання коригувальних коефіцієнтів і довідникових графічних функцій. Надана методика чисельно-польового аналізу і отримані результати розрахунку опорів обмоток та механічної характеристики рекомендуються як основа для удосконалення системи проєктування ТАД.

Some major problems in the motor drive are the overshoot or undershoot of transient response characteristics and a parameter mismatch due to magnetic saturation. This study proposed a 3D inductance map combined with a maximum-torque-per-ampere (MTPA) map based on a finite-element (FE) motor model considering a cross-coupling magnetic saturation impact to overcome this problem. The proposed FE motor model has a high accuracy of no-load back electromotive force (e.m.f.) around 98.3% compared to the measurement results. Then, nine scenarios of vector control combinations of inductance maps and current supply variations of β 0°, 45°, and MTPA were investigated. As a result, the transient response improvement for β 0°, 45°, and MTPA without the map and with Ld and Lq maps is 63%, 10%, and 15%, respectively. Moreover, for the steady-state response, the average torque improvement between MTPA and Idref 0 A control is 9.21%, 8.97%, and 8.98% for the no-map, ave-map, and 3D-inductance-map conditions, respectively. The MTPA trajectory characteristic was also updated to illustrate the actual MTPA condition compared to the conventional MTPA control. In detail, the proposed method has reduced the parameter mismatch for the current control loop in the transient state and improved the MTPA control trajectory for the steady-state response. Finally, the improvement of vector control characteristics of the proposed method was verified by an FE simulation and experimental measurement results.

The synchronous reluctance motor (SynRM) has significant nonlinear characteristics due to the problems of magnetic saturation and cross-coupling and the poor adaptability of the general controller to parameter changes seriously affects the control performance of the motor. In order to solve the above problems, this paper proposed a control system for the SynRM with a brain emotion controller based on empirical information to solve the motor control problem of magnetic saturation. Firstly, the nonlinear mathematical model of the SynRM considering magnetic saturation is established by introducing the magnetic saturation parameter. Secondly, the sensory input function and emotional cue function based on systematic error are given and the vector control system of the SynRM considering magnetic saturation is designed. The influence of the parameters and the learning rate of the brain emotional learning based intelligent controller (EI-BELBIC) on the adjustment range of the controller parameters is studied. Then the SynRM is controlled under different working conditions and the control effect is observed. The results show that the designed vector control system of the SynRM based on EI-BELBIC has strong reliability, accurate control, rapid response, and strong anti-interference ability under magnetic saturation.

The magnetic saturation of iron‐core will reduce the maximum output force, influence the linear force characteristic and control precision of the magnetic bearing. To avoid these problems, a modified iron‐core design rule for the alternating‐pole magnetic bearing is proposed. The thickness of both stator yoke and rotor journal should be designed as 3/4 of the stator pole width for the alternating‐pole configuration, which is successfully verified by 3D finite element method and experiments. Based on the improved design, the structural sizes, rotor iron losses, and force coupling characteristics of the paired‐pole configuration and the alternating‐pole configuration are compared. The results show that the size of the alternating‐pole bearing is smaller than that of the paired‐pole bearing; the alternating‐pole configuration generates slightly higher rotor iron loss than the paired‐pole configuration; the coupling strength of the alternating‐pole configuration is stronger than that of the paired‐pole configuration irrespective of whether the magnetic force coupling is caused by rotor displacements or control currents. The presented method and results can provide a reference for the design and selection of the active magnetic bearings.

Purpose The authors derive a nonlinear MOR based on the Cauer ladder network (CLN) representation, which serves as an application of the parameterized MOR. Two parametrized CLN representations were developed to handle the nonlinear magnetic field. Simulations using the parameterized CLN were also conducted using an iron-cored inductor model under the first-order approximation. Design/methodology/approach This work studies the effect of parameter variations on reduced systems and aims at developing a general formulation for parametrized model order reduction (MOR) methods with the dynamical transition of parameterized state. Findings Terms including time derivatives of basis vectors appear in nonlinear state equations, in addition to the linear network equations of the CLN method. The terms are newly derived by an exact formulation of the parameterized CLN and are named parameter variation terms in this study. According to the simulation results, the parameter variation terms play a significant role in the nonlinear state equations when reluctivity is used, while they can be neglected when differential reluctivity is used. Practical implications The computational time of nonlinear transient analyses can be greatly reduced by applying the parameterized CLN when the number of time steps is large. Originality/value The authors introduced a general representation for the dynamical behavior of the reduced system with time-varying parameters, which has not been theoretically discussed in previous studies. The effect of the parameter variations is numerically given as a form of parameter variation terms by the exact derivation of the nonlinear state equations. The influence of parameter variation terms was confirmed by simulation.

This article presents the process of building a hybrid analytical model (HAM) for surface-mounted permanent-magnet machines. The HAM couples a reluctance network (RN) model in the stator region with a magnetic scalar potential analytical model in the air gap and magnets regions. This hybrid model can deal with the slotting effect with straight teeth, and takes magnetic saturation into account in the stator iron material using the RN model. It is calculated under open-circuit and loaded conditions. The magnetic flux density, flux linkage, back electromotive force (EMF), and torque of the machines are also calculated. This hybrid model is compared with the subdomain method. It is also compared with the finite element method (FEM) both in terms of the size of the matrix that needs to be calculated and in terms of the torque error. We analyzed this method for two surface-mounted permanent-magnet machines, one with a symmetry factor of four and another with a symmetry factor of three. In both cases, HAM reduced the size of the matrix that needed to be solved compared to FEM. In the machine with a symmetry factor of three, when the matrix size of both FEM and HAM was around 1700 × 1700, the torque error of FEM was 2.62% compared to the high-mesh-density FEM simulation, while the torque error of HAM was only 0.17% compared to the same simulation. HAM also had significant advantages over the subdomain method, as it reduced the torque error from 16.8% to 0.08% in the case of high magnetic saturation. The HAM can, hence, play a significant role in the design and optimization of surface-mounted permanent-magnet machines, especially in cases where magnetic saturation is present.

This paper presents the design and an analysis of a surface PM vernier generator (SPMVG) for MW-scale direct-drive (DD) wind turbine application. An SPMVG has the advantage of higher torque density; however, especially at higher power ratings with increased electrical loadings, the power factor worsens and there are some serious concerns including magnetic saturation of cores and PM demagnetization. These issues are directly related to machine design parameters such as PM dimensions, applied electrical loading, slot geometry and the choice of slot–pole combination. It is determined that depending on the PM thickness and a few other design variables, each slot–pole combination has an optimal value of specific electrical loading. The use of the optimal value of specific electrical loading ensures that the machine is not saturated, the performance is optimum and the power factor is not unnecessarily degraded. Moreover, under certain design constraints, design criteria are developed that ensure the proper choice of various entailed design variables. By using the developed design criteria, the trends of various electromagnetic performances with variation in the slot–pole combination are discussed. The obtained trends clearly show that each slot–pole combination offers a certain torque density and power factor; thus, it serves as a guide for the selection of the slot–pole combination considering the required torque density and/or certain power factor limit. Finally, by using the developed design approach, an SPMVG for rated power of 15 MW is designed; the design objectives are to maximize torque per volume with a power factor limit of 0.4. Moreover, the various aspects of the performances of the designed SPMVG are comprehensively compared against a conventional PM DD 15 MW generator.

Permanent magnet synchronous machines (PMSMs) have garnered increasing interest because of their advantages such as high efficiency, high power density, wide speed range, and fast dynamics. They have been employed recently in several industrial applications including robotics and electric vehicles (EVs). However, PMSMs have highly nonlinear magnetic characteristics, especially interior PMSMs, due to the existence of reluctance torque. Nonlinearity complicates not only machine modeling but also control algorithms. An accurate machine model is the key aspect for the prediction of machine performance as well as the development of a high-performance control algorithm. Hence, this paper presents an accurate modelling method for PMSMs. The proposed model method is applicable for all PMSMs, even multiphase machines. This paper considers a fractional slot concentrated winding 12/10 interior PMSM (IPMSM) for this study to demonstrate the effect of magnetic saturation and special harmonics. The developed model considers accurately the magnetic saturation, mutual coupling, spatial harmonics, and iron loss effects. It utilizes finite element analysis (FEA) to estimate the precise magnetic characteristics of IPMSM. The finite element model is calibrated precisely using experimental measurements. The iron losses are estimated within the simulation model as d- and q-axes current components. The model accuracy is validated experimentally based on a 12/10 IPMSM prototype.

U ovome diplomskom radu opisan je postupak izvođenja jednadžbi sinkronog stroja s istaknutim polovima na rotoru za dvoosni rotirajući 𝑑𝑞 sustav. Prikazane su i objašnjene jednadžbe transformacija Clarke i Park. Objašnjen je postupak primjene nelinearnog magnetskog zasićenja sinkronog stroja u 𝑑-osi istoimenog sustava. Prikazana je primjena simulacije stroja u programskom okruženju PLECS te su komentirani dobiveni rezultati za slučajeve praznog hoda i udarnog priključenja tereta u određenom vremenskom trenutku. Rezultati simulacije su temeljeni na odzivima struja, elektromagnetskog momenta i mehaničke brzine vrtnje., This thesis describes the procedure for deriving the equation of a synchronous machine with salient poles on the rotor for a two-axis rotating 𝑑𝑞 system. The transformation equations of Clarke and Park are presented and explained. The application procedure of nonlinear magnetic saturation of the synchronous machine in the d-axis of the system. The application of machine simulation in the PLECS software environment is presented and the results obtained for the cases of idling and shock connection of the load at a certain point in time are commented. The simulation results are based on the responses of currents, electromagnetic torque and mechanical rotation speed.

In this study, we established the nonlinear model order reduction (MOR) of induction motors by parameterizing a multi-port Cauer ladder network (CLN). Appropriate parameters were selected to incorporate nonlinear magnetic characteristics. The parameterized multi-port CLN was applied to the transient analysis of a rotating induction motor. The proposed method reproduced the finite-element analysis results with various driving frequencies and slips. The parameterized multi-port CLN can effectively reduce the computation time for analyses requiring a large number of time steps.

Recently, maintenance applications around power lines have been actively studied. These applications usually supply power through magnetic energy harvesting(MEH) to devices around the power line. A major challenge for practical MEH is to overcome magnetic saturation, which can cause degradation of power density under a wide current range in the power line. In this paper, we propose a design methodology to harvest maximized output power by considering the saturation effect. To consider magnetic saturation, the output power model and the saturable magnetizing inductance model based on magnetizing current were comprehensively analyzed. Additionally, the critical point of saturation for the maximum harvested power was analyzed by considering different primary side current conditions. With the proposed design methodology, the accuracy and efficiency of the output model were verified with experimental results compared to the conventional model. To consider the real environment, a 150 kW class of AC resistor load bank was implemented to control the primary current from 0 to 100 A with power frequency of 60 Hz. Experimental results show that the proposed method can harvest an average power of 14.32 W on 70 A power line, which is an increase of 39.8 % compared with the conventional design method.

In recent years, an expansive research exertion has been devoted to the control for aeorogenerators conforming of a Doubly Fed Induction Generator (DFIG) coupled to a wind turbine. Most preceding controllers based on standard models (whose magnetic induction characteristic is considered linear and iron losses have not been taken into account). Since such a magnetic characteristic is nonlinear in practice, this work develops a variable speed control strategy on the basis of a DFIG model in presence of nonlinear magnetic characteristic and iron losses. The main contribution of this paper is to present a high-performance maximum power point (MPPT) control of DFIG based on rotor flux optimization, designed to reach an optimal operational conditions. Of the foregoing, the control goal is twofold: i) minimization of the stator and rotor currents circulating by controlling the rotor flux for a maximum electromagnetic torque; ii) captured the maximum wind power to insure the attainment of MPPT. The performances of the proposed command has been studied theoretically and validated by simulation studies with Matlab/Simulink.

This article proposes a nonlinear controller based on feedback linearization (FL) for synchronous reluctance motor (SynRM) drives which takes into consideration the magnetic saturation. The proposed nonlinear FL control based control technique has been developed starting from the theoretical definition of an original dynamic model of the SynRM taking into consideration both the self- and the cross-saturation effects. Such a control technique permits the dynamics of both the speed and axis flux loops to be maintained constant independently from the load and the saturation of the iron core in both constant flux and variable direct axis flux operating conditions. Finally, sensitivity of the performance of the proposed FL control versus the variation of the main motor parameters has been verified. The proposed technique has been tested experimentally on a suitably developed test setup. The proposed FL control has been further compared with the classic field-oriented control (FOC) in both constant flux and variable flux working conditions.

Metallic glasses produced with Selective Laser Melting (SLM) often contain internal mechanic stress. This internal stress can have an impact on the magnetic properties of the material due to its connection to the magnetic anisotropy of the material. Therefore the effect of different heat treatments aimed to reduce the effect of internal stress on the magnetic properties of an Fe-based Metallic Glass (MG) and how this relates to the crystallization of the material was examined in this project. The magnetic properties were measured with a Vibrating Sample Magnetometer (VSM) and the Longitudinal Magneto-Optic Kerr Effect (L-MOKE) and structural changes to the material from the heat treatments, such as crystallization, was examined with X-Ray powder Diffraction (XRD) before and after heat treatment. From the measurements we found that heat treatments close to and above the crystallization temperature Tx lead to crystallization and a decrease in magnetic saturation MS. Heat treatments below Tx around 430°C showed a smaller reduction in MS but did not show any crystallization. The measurements with L-MOKE showed no consistent change in coercivity so no conclusion could be drawn from these. Metallglas som tillverkats med den additiva tillverkningstekniken Selective Laser Melting (SLM) innehåller ofta interna mekaniska spänningar. Dessa spänningar kan på grund av deras koppling till materialets magnetiska anisotropi ha en påverkan på materialets magnetiska egenskaper. I detta projekt har därför effekten av olika värmebehandlingar utförda för att minska de interna spänningarnas påverkan på de magnetiska egenskaperna av ett Fe-baserad metallglas och hur detta relaterar till kristalliseringen av materialet undersökts. De magnetiska egenskaperna av materialet mättes med en Vibrating Sample Magnetometer (VSM) och Longitudinal Magneto-Optic Kerr Effect (L-MOKE). Strukturella förändringar, så som kristallisering, hos materialet orsakade värmebehandlingarna undersöktes med X-Ray powder Diffraction (XRD). Samtliga mätningar genomfördes före och efter värmebehandling. Från mätningarna fann vi att värmebehandlingar nära kristalliseringstemperaturen Tx gav kristalltillväxt samt minskade mättnadsmagnetisering MS. Värmebehandlingar under Tx runt 430°C gav en lägre reducering av MS samt gav ej någon kristalltillväxt. L-MOKE-mätningarna gav ingen konsekvent förändring i materialets koercivitet och inga slutsatser kunde därmed dras från dessa.

MEng (Electrical and Electronic Engineering), North-West University, Potchefstroom Campus In 2019, an article published by Geldenhuys and Padayachee reported unexpected overvoltages during the commissioning phase of distribution transformers. Consequently, resonance was reported as the cause of overvoltages on the secondary winding when the expected voltage was 0 V. Recent changes to the SANS 780 standard mandated a reduction in distribution transformer core losses, which made the overvoltages even worse. Geldenhuys and Padayachee claim to have only scratched the surface of the problem. A hypothesis was developed that the unexpected overvoltages could be caused by ferroresonance and a research study was launched to investigate the resonance phenomenon found in 32 kVA, 22/0.4 kV distribution transformers complying with the new SANS 780 standard of 2019. Ferroresonance is a nonlinear form of resonance involving a saturable inductor and a capacitor. Ferroresonance was first identified and described in 1914. Consequently, a vast amount of resources is available on the topic. Despite extensive studies in this field, ferroresonance is still poorly understood in the scientific community. This work provides a lengthy critical review of the literature on this topic. The literature on ferroresonance proves that the initiation of ferroresonance is strongly dependent on a wide variety of factors. One of these is remnant flux. The remnant flux dependence makes the modelling of ferroresonance particularly difficult. Accurate ferroresonance studies require a detailed hysteresis model which can store remnant flux upon de-energization. Consequently this work also contains a detailed study on hysteresis, which could be a study all on its own. The most prominent hysteresis models from this study are the Jiles-Atherton, Preisach and Tellinen models. The Tellinen model is the most elementary of these models and its implementation is straightforward. The Preisach model is the most complex and also the most accurate. The Jiles-Atherton model is most often used in literature since it is less involved than the Preisach model while still retaining the ability to model minor loops and remnant flux. Chapter 3 develops Tellinen and Jiles-Atherton hysteresis models and replicates results found in the literature. An important outcome in the study of ferroresonance proves that the π-transformer model is superior to the traditional T-model for the modelling of ferroresonance. Chapter 3 of this report replicates results found in literature and builds on the π-model to develop an accurate representation of the transformer being studied. The π-model is developed even further by considering not only the standard Open-Circuit (OC) and Short-Circuit (SC) transformer tests, but also the Sweep Frequency Response Analysis (SFRA) of the transformer. The SFRA allows the user to define a parallel capacitance across the magnetization branch of the transformer model, which significantly improves its frequency behaviour up to 10 kHz. These capacitances are typically neglected for a lack of transformer design data. Chapter 3 also contains a detailed discussion on the use of peak vs Root Mean Squared (RMS) data points for simulation and the effect that high harmonic content can have on the modelling of a nonlinear inductor. Despite replicating hysteretic results in the literature, neither the Tellinen model nor the Jiles-Atherton model could accurately represent the transformer being studied. High harmonic content during the OC test presented numerous hurdles which could not be overcome. Numerical errors limited the use of the Tellinen model, while parameter determination was problematic for the Jiles-Atherton model. This is despite the use of Particle Swarm Optimization (PSO) to determine the 5 parameters of the Jiles-Atherton model. The developed π-model is used in Chapter 4 and Chapter 5 to conduct switching studies of the single-phase transformer in a power system. The overvoltages reported by Geldenhuys and Padayachee are replicated and independent studies show that the transformer is susceptible to ferroresonance. Bifurcation diagrams are used to investigate the effect of a variation in parameters on the ferroresonance of the transformer. However, simulations prove beyond doubt that ferroresonance is not the cause of the overvoltages in the power system. Two main reasons can be provided for this conclusion: 1) low line-to-ground voltage during single-phase switching and 2) low internal capacitance of the transformer. Chapter 5 proceeds to discuss three different mitigation strategies to reduce the overvoltages initiated by single-phase switching. The report concludes by making recommendations for future improvements, such as alternative cost functions for the PSO algorithm. This will allow hysteresis and remnant flux to also be taken into consideration. Several appendices provide proofs of errors in literature, MATLAB code, simulation data points and an article presented by the author at the 2021 South African Universities Power Engineering Conference. Masters

Nowadays, electrical drives require more and more precision and reliability. Induction machine is one of the most robust actuators in terms of maintenance and reliability. Their control requires a good knowledge of the physical phenomena governing its operation. Saturation and heating are two main phenomena that must be taken into account to achieve the desired performance. In this paper, we will synthesize a nonlinear control law based on the “Backstepping” method, to regulate rotor speed and flux. This law takes into account saturation and rotor resistance variation effects. The immunity of the control to temperature rise will be tested. This control strategy is studied by simulation in the MATLAB/Simulink environment.

An exhaustive characterization of the physicochemical properties of gum arabic (GA)-coated Fe3O4 magnetic nanoparticles was conducted in this work. These nanoparticles were obtained via the in-situ coprecipitation method (a fast single-step method) in two GA:Fe ratios, 10:1 and 20:1, respectively. Several experimental techniques were applied in the characterization process, all of them described below. Using Transmission Electron Microcopy images, they were shown to have spherical-like morphology with 11 nm diameter. The Fourier Transform Infrared spectra confirmed the attachment of the GA on the surface of the magnetic nanoparticles (MNPs), providing good colloidal stability from pH 7 to 8. The thickness of the coatings (1.7 nm and 1.1 nm) was determined using thermogravimetric measurements. A high specific absorption rate and superparamagnetic properties were determined using alternant and static magnetic fields, respectively. The GA-coated MNPs were non-cytotoxic, according to tests on HT-29 human intestine cells. Additionally, HT-29 cells were exposed to magnetic fluid hyperthermia at 530 kHz, and the induction of cell death by the magnetic field, due to the heating of GA-coated MNP, was observed.

In this paper, intelligent control of a reluctance synchronous motor by an emotional controller, considering the effect of magnetic saturation on implementation, is analyzed, the maximum torque per ampere (MTPA) strategy is provided. According to the application of the proposed control scheme, the structure adequately performs the control of speed and magnetic flux of the reluctance synchronous motor drive. Additionally, the application of intelligent control based on an emotional learning system has provided adequate results to create a proper control process. The control function of a SynRM drive based on vector control in a rotor machine was compared with another based on emotional controllers and a PI controller regulated by genetic algorithms. The result of this comparison was the improvement of control functions by the controller based on the emotional controller. In addition, the MTPA based on search algorithms was well implemented in different situations. Due to its simplicity and independence from system parameters, the emotional controller can be considered as a potential operational method in the industry.

Recently, a motor for an in-wheel system—which is advantageous when applied to electric vehicles and self-driving systems—has received much attention. In this paper, we propose an analysis and design method that can be used for an in-wheel motor. In-wheel motors require high torque density and a compact form factor to be wheel-mounted. To meet these requirements, an axial flux permanent magnet motor is proposed for the in-wheel system. The end-winding length of the coil is a key factor to be considered in this design. Hence, we propose a novel method to study the end-winding length. Due to the structural characteristics of an axial flux permanent magnet motor, a three-dimensional finite element analysis, which requires much time and expense, is essential. To solve this problem, we propose a novel analytical method combined with finite element analysis to mitigate the time and cost factors in the development of the axial flux permanent magnet motor. The magnetic saturation and the slot opening effect, which are considered during the analysis and design phase, are extremely difficult to analyze due to their nonlinearity. Therefore, a novel analytical method and algorithm, which can consider nonlinear effects, such as the magnetic saturation and slot opening, is proposed. The usefulness of the proposed analysis and design method and the axial flux permanent magnet motor for an in-wheel system were verified via 3D finite element analysis using a commercial simulation tool (JMAG).

High-frequency injection (HFI) is widely used for zero-to-low speed self-sensing in machines with saliency. HFI algorithms use inductive saliency in the d- and q-axes to estimate the rotor position in permanent magnet synchronous machines (PMSMs). Generally speaking, surface PMSMs (SPMSMs), which are designed without inductive saliency, are not suitable for HFI inductive based self-sensing. In this article, a method to enhance HFI algorithms at zero-to-low speed for classically designed SPMSMs with low inductive saliency is presented. The proposed method is based on using intentional magnetic saturation under flux-intensifying (FI) operation, which will temporarily enable robust self-sensing operation in the zero-to-low speed region in machines that are not suitable for traditional HFI self-sensing.

The direct axis (d-axis) stator winding and field winding of a wound-rotor synchronous motor (WRSM) are mutually coupled much like the primary and secondary windings in a transformer are. As the field winding has a large number of turns, small variations of the stator d-axis current can induce a great electromotive force (EMF) in the field windings. This induced EMF voltage disturbs field current regulation, invokes an unwanted field current response, and distorts the stator d-axis flux. In this work, a novel field current control strategy for the WRSM is proposed for compensating the disturbance by d-axis current in field winding. The coupling effect between the stator d-axis winding and field winding is analyzed by using a polynomial regression of the stator d-axis flux linkage. Based on an analysis of the coupling effect, the proposed strategy combines two control methods. First, feedforward control is applied to decouple the field current response from the coupled change in the stator d-axis current flux. Second, a method is used to adjust the d-axis current to ensure that the field inverter voltage is not saturated. Simulations and experiments are presented to verify the proposed control method, proving that the proposed field current control strategy successfully compensates for the field current ripples caused by variations in the coupled stator d-axis current flux.

Shaded-pole induction motors (SPIMs) are extensively used in industrial applications, home appliances and ventilation systems due to their simple structure, low cost and low maintenance requirement. Formation of elliptic rotating field in SPIM makes its analysis rather complex. As the result of this complexity, there are relatively limited publications on the theory, design and analysis for this kind of motor. In many cases, its design is based on trial and error method. As it is appreciated, the accuracy of predicted performance of electric machines is closely related to the accuracy of the winding inductances used in calculations. For this reason, in this study, stator and shading-rings end-winding leakage inductance, stator winding self-inductance, total leakage inductance of the stator winding and the mutual inductance between stator and rotor winding of a 4-pole SPIM are obtained by means of the derived analytical equations and real-time experiments. Also, the effect of magnetic saturation on the stator self and leakage inductances, and the variation of stator-rotor mutual inductance with respect to the rotor position have been investigated. At the end of the study, the accuracy of computed stator winding self-inductance is validated by an experimental exercise.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES This Ph.D. thesis provides contributions to the design of robust current controllers for grid-connected converters, including: i) a time-varying model to deal with the magnetic soft saturation in the filter inductors and the possible variation of the grid impedance; ii) systematic procedures to design the gains of state feedback controllers robust against magnetic soft saturation, obtained by means of linear matrix inequalities; iii) an optimization of the performance of controllers by means of pole location robust against uncertainties in the grid impedance, taking into account a trade-off between transient performance and control effort. For the design of the robust controllers, the plant is modeled in a polytopic way, in the discrete time domain, including the delay due to the digital implementation of the controller. An arbitrary number of resonant controllers are also included to ensure tracking of sinusoidal references and rejection of harmonic disturbances from the grid voltages, for instance. In the sequence, two strategies based on linear matrix inequalities (robust pole location and H2 guaranteed cost) are used to obtain robust state feedback gains. These gains are implemented in practice in a digital signal processor, leading to real-time simulation results based on hardware-in-the-loop and also on experimental results based on a prototype which exhibit high quality transient and steady state performances. The currents injected into the grid meet the requirements of the IEEE 1547 Standard, in the case of magnetic soft saturation of the filter inductors, and also in the case of uncertain and possibly time-varying grid impedances. Este trabalho apresenta contribuições ao projeto de controladores robustos de corrente para conversores conectados à rede, incluindo: i) uma modelagem variante no tempo para tratar a saturação magnética suave nos indutores do filtro e a possível variação da impedância da rede; ii) procedimentos sistemáticos para o projeto dos ganhos de controladores por realimentação de estados que sejam robustos à saturação magnética, obtidos utilizando desigualdades matriciais lineares; iii) uma otimização do desempenho de controladores por alocação de polos robusta a incertezas na impedância de rede, levando em consideração uma relação de compromisso entre desempenho transitório e esforço de controle. Para o projeto de controladores robustos, a planta é modelada de forma politópica, no domínio do tempo discreto, incluindo o atraso referente à implementação digital do controlador. Também são incluídos controladores ressonantes de dimensão arbitrária para garantir rastreamento de referências senoidais e rejeição de distúrbios harmônicos provenientes, por exemplo, da tensão da rede elétrica. Na sequência, duas estratégias baseadas em desigualdades matriciais lineares (alocação robusta de polos e custo garantido H2) são utilizadas para a obtenção de ganhos robustos de realimentação de estados. Estes ganhos são implementados na prática em um processador digital de sinais, levando a resultados de simulação em tempo real baseados em hardware-in-the-loop e a resultados experimentais baseados em protótipo físico que exibem boa qualidade em transitórios e em regime permanente. As correntes injetadas na rede atendem a requisitos da norma IEEE 1547, no caso de saturação magnética suave dos indutores do filtro, e também no caso de incertezas e possível variação na impedância de rede.

In the permanent magnet synchronous motor (PMSM) sensorless drive method, motor inductance is a decisive parameter for rotor position estimation. Due to core magnetic saturation, the motor current easily invokes inductance variation and degrades rotor position estimation accuracy. For a constant load torque, saturated inductance and inductance error in the sensorless drive method are constant. Inductance error results in constant rotor position estimation error and minor degradations, such as less optimal torque current, but no speed estimation error. For a periodic load torque, the inductance parameter error periodically fluctuates and, as a result, the position estimation error and speed error also periodically fluctuate. Periodic speed error makes speed regulation and load torque compensation especially difficult. This paper presents an inductance parameter estimator based on polynomial neural network (PNN) machine learning for PMSM sensorless drive with a period load torque compensator. By applying an inductance estimator, we also proposed a magnetic saturation compensation method to minimize periodic speed fluctuation. Simulation and experiments were conducted to validate the proposed method by confirming improved position and speed estimation accuracy and reduced system vibration against periodic load torque.

When developing three-phase drives for Electric Vehicles (EVs), it is essential to verify the controller design. This will help in understanding how fast and accurately the torque of the motor can be controlled. In order to do this, it is always better to test the controller using the software version of the motor or vehicle drivetrain than using actual hardware as it could lead to component damage when replicating extreme physical behavior. In this thesis, plant modelling of Permanent Magnet Synchronous Machine (PMSM) and vehicle drivetrain in MATLAB/Simulink for Model Based Design (MBD) is presented. MBD is an effective method for controller design that, if adopted can lead to cost savings of 25%-30% and time savings of 35%-40% (according to a global study by Altran Technologies, the chair of software and systems engineering and the chair of Information Management of the University of Technology in Munich) [1]. The PMSM plant models take effects like magnetic saturation, cross- coupling, spatial harmonics and temperature into account. Two PMSM models in d-q frame based on flux and inductance principles were implemented. Flux, torque maps from Finite Element Analysis (FEA) and apparent inductance from datasheets were used as inputs to the flux- and inductance-based models, respectively. The FEA of PMSM was done using COMSOL Multiphysics. The PMSM model results were compared with corresponding FEA simulated results for verification. A comparison of these PMSM models with conventional low fidelity models has also been done to highlight the impact of inclusion of temperature and spatial harmonics. These motor models can be combined with an inverter plant model and a controller can be developed for the complete model. Low frequency oscillations of drivetrain in EVs lead to vibrations which can cause discomfort and torsional stresses. In order to control these oscillations, an active oscillation damping controller can be implemented. For implementation of this control, a three-mass mechanical plant model of drivetrain with an ABS (Anti-lock Braking System) wheel speed sensor has been developed in this thesis. Analysis of the model transfer function to obtain the pole zero maps was performed. This was used to observe and verify presence of low frequency oscillations in the drivetrain. In order to include the effects of ABS wheel speed sensor and CAN communication, a model was developed for the sensor. Testning av regulatorernas inställningar med hänsyn till snabbhet och noggrannhet i momentreglering är avgörande i trefasiga drivsystem för elektriska fordon. Oftast är det bättre att simulera i stället för att utföra experimentella tester där komponenter kan skadas på grund av fysisk stress. Detta kallas för Model Based Design (MBD). MBD är an effektiv metod för utformningen av styrningen som kan leda till kostnadsbesparingar på 25%-30% och tidsbesparingar på 35%-40% enligt en studie från Altran Technologies i samarbete med Tekniska universitet i München, TUM. Detta examensarbete behandlar en modell för en synkronmaskin med permanentmagneter (PMSM) samt en modell för drivlinan utvecklad i Matlab/Simulink för MBD. PMSMs modellen inkluderar magnetisk mättnad och tvärkoppling, MMF övervågor och temperatur. Två PMSM modeller har utvecklats. Den första baseras på magnetiskt flöde som erhålls från finita element beräkningar i COMSOL Multiphysics medan den andra bygger på induktanser givna från datablad. En jämförelse av dessa PMSM-modeller med konventionella low fidelity-modeller har också gjorts för att illustrera påverkan temperaturberoende och MMF övervågor. Modellerna kan kombineras med en växelriktarmodell för att utveckla en hel styrenhet. Lågfrekventa oscillationer i drivlinan leder till vibrationer som kan orsaka vridspänningar och försämra komforten i elfordonet. En aktiv dämpningsregulator kan implementeras för att kontrollera spänningarna men en mekanisk drivlinemodell med tre massor och en ABS (anti-lock braking system) hastighetssensor behövs. Den mekaniska modellen har implementerats och analyserats även beaktande en modell för en CAN kommunikationskanal. Oscillationer med låg frekvens kunde observeras i modellen.

Conventional polyurethane foam has non-tunable sound absorption properties. Here, a magneto-induced foam, called magnetorheological (MR) foam, was fabricated with the feature of being able to tune sound absorption properties, primarily from the middle- to higher-frequency ranges. Three different samples of MR foams were fabricated in situ by varying the concentration of Carbonyl Iron Particles (CIPs) (0, 35, and 75 wt.%). The magnetization properties and tunable sound absorption characteristics were evaluated. From the magnetic saturation properties, the results showed very narrow and small coercivity of hysteresis loops relative to the soft magnetic properties of the CIPs. MR foam with 75 wt.% CIPs showed a higher magnetic saturation at 91.350 emu/g compared to MR foam with 35 wt.% CIPs at 63.896 emu/g. For tunable sound absorption testing, the effect of &lsquo, shifting&rsquo, to higher frequency was also observed when the magnetic field was applied, which was ~10 Hz for MR foam with 35 wt.% CIPs and ~130 Hz for MR foam with 75 wt.% CIPs. As the latest evolution of semi-active noise control materials, the results from this study are valuable guidance for the advancement of MR-based devices.

The accurate initial rotor position of a permanent magnet synchronous motor (PMSM) is necessary for starting the motor, and for the position sensorless control method adopted by a PMSM control system under some working conditions. This paper presents a new method to detect the initial rotor position of a permanent magnet synchronous motor (PMSM). The method does not need a low-pass filter, and has strong robustness and a simple calculation method. According to the relationship between high-frequency current response and rotor position angle &theta, the rotor position angle can be obtained by arctangent and linear formulae. Finally, the magnetic polarity of the rotor is distinguished according to the change of inductance. In this method, the arctangent function is used to eliminate the filtering process and reduce the influence of the parameter deviation of the motor system on the detection accuracy of the initial position. The experimental results verify the correctness of the theoretical analysis and the effectiveness of the method.

This paper presents a saturable analytical model of induction machines, with a systematic approach for segregating the electromagnetic losses. The proposed model is based on the equivalent circuit of the machine, which has been augmented to account for different loss components. The segregation of different loss components in stator and rotor have been improved by considering the loading, skin effect and field-weakening operation. The required parameters of the model are identified from a well-defined set of finite element analysis of the machine. The proposed model and the identification methodology have been tested on two different induction machines. In both cases, the finite element computations are validated with laboratory measurements, and the analytical model is validated against the finite element model. The results show that the proposed model is more accurate than the conventional ones from the literature, and thus it can be used as a component while building a digital twin of the induction machine, and inserted into a virtual simulation software for real-time thermal management for example.

This paper presents the optimization of sensorless sliding-mode control for induction motor, considering magnetic saturation effects. A five-order sliding-mode observers and estimators are elaborated to replace the sensors of an induction motor. The proposal is based on double optimization of sensorless sliding mode control of an induction motor in the point of view of dynamic and energetic performances. In order to obtain better performances of the proposed control method, Particle Swarm Optimization (PSO) algorithm is used notably to determine the optimal gains of the observers as well as the optimal parameters of the regulators. Regarding the energetic optimization, the reference of the rotor flux is generated using another developed algorithm that permits us to dynamically determine the optimal rotor flux for each given value of motor load and speed. As results, sensorless sliding mode control takes into account all operating ranges of the machine from very low speeds, low speeds, to high speed with or without load. Numerical simulations are carried out each time to confirm theoretical predictions.

A millifluidic reactor with a 0.76 mm internal diameter was utilized for the synthesis of monodisperse, high magnetic moment, iron carbide (FexCy) nanoparticles by thermal decomposition of iron pentacarbonyl (Fe(CO)5) in 1-octadecene in the presence of oleylamine at 22 min nominal residence time. The effect of reaction conditions (temperature and pressure) on the size, morphology, crystal structure, and magnetic properties of the nanoparticles was investigated. The system developed facilitated the thermal decomposition of precursor at reaction conditions (up to 265 °C and 4 bar) that cannot be easily achieved in conventional batch reactors. The degree of carbidization was enhanced by operating at elevated temperature and pressure. The nanoparticles synthesized in the flow reactor had size 9–18 nm and demonstrated high saturation magnetization (up to 164 emu/gFe). They further showed good stability against oxidation after 2 months of exposure in air, retaining good saturation magnetization values with a change of no more than 10% of the initial value. The heating ability of the nanoparticles in an alternating magnetic field was comparable with other ferrites reported in the literature, having intrinsic loss power values up to 1.52 nHm2 kg–1.

In this paper, an accurate analytical subdomain model to calculate electromagnetic performances of bearingless flux-switching permanent magnet (BFSPM) machines is developed. The entire region of the machine is divided into six subdomains, including slots, air gap, magnets, and so on. According to the Neumann boundary conditions between the subdomains and the iron and the continuity conditions at the interface between the adjacent subdomains, the magnetic field distributions of subdomains are obtained by solving the Maxwell equations. In addition, a method to compensate the saturation effect is proposed, and the magnetic saturation of the stator and rotor is considered by the actual B-H characteristics. Based on the proposed analytical method, the air-gap flux density distributions of the machine with different iron material under linear and nonlinear conditions are predicted. Further, the electromagnetic performances including the cogging torque, electromagnetic torque, flux linkage, back-EMF, inductance, and suspension force are calculated. These analytical results are compared with those obtained by the Finite Element Analysis (FEA) to verify the accuracy of the proposed analytical method.

In order to solve problems associated with inductance parameter changes on traditional maximum torque per ampere (MTPA) control method for interior permanent magnet synchronous motor, such as large amount of computation, complicated control system, and low control precision, an MTPA control method based on inductance segmentation is proposed. Considering the effects of magnetic saturation, the inductance parameters are processed by segmentation analysis. The Newton iteration method is used to solve the correspondence between the electromagnetic torque and the optimum ${d}$ – ${q}$ axis current components, and the subsection curve is fitted to achieve MTPA control. By analyzing and processing inductance parameters, this control method improves the accuracy of control system. The ${d}$ – ${q}$ axis current reference is realized by piecewise curve fitting to improve the dynamic performance of the system. Finally, the dynamic performance of this method is compared with that of the traditional method through simulation and experiment. The simulations and experiments results show that this method has the advantages of fast dynamic response, high control accuracy, and simple implementation.

This paper describes an interior permanent magnet synchronous motor (IPMSM) based on a new adjustable field method. The proposed PM motor achieved magnetic field control utilizing magnetic saturation. In this paper, a back electromotive force (e.m.f.) measurement test and a load test using the prototype motor were conducted to clarify if the proposed motor had a wide operation range. In the back e.m.f. measurement test, it was confirmed that the proposed motor had a wide magnetic field controllable range of 51.7%. In addition, it was revealed, through the load test, that the proposed motor had a wide operating range, including both low-speed high-torque and high-speed low-torque driving conditions. Moreover, based on electromagnetic field analysis, the magnetic field control performance of the proposed adjustable field method was compared with the conventional field weakening control and other adjustable field methods. As a comparison result, it was verified that the proposed motor had less copper loss for the magnetic field control and fewer losses in the high-speed operating range.

This paper deals with an analytical model of reluctance synchronous motor, able to consider both stator slotting effect and magnetic saturation in the stator and rotor iron paths. It joints the field distribution at the air gap to a lumped-parameter magnetic network. Local saturation factors are defined so as to adjust the flux-density distribution. The analytical approach exhibits great potentiality, since it is a formulation based on an harmonic study, and it is easily adaptable to any motor geometries. As an example, 36-slot 4-pole machine is analyzed, considering three flux barriers per pole. Finite element analysis confirms the results achieved by means of the analytical model.

This paper deals with a dynamic model for three-phase induction machines equipped with closed rotor slots and deep rotor bars. The thin bridges closing the rotor slots saturate highly as a function of the rotor current. The impedance of the rotor bars also varies much as a function of the rotor current frequency. An extended dynamic model, which takes into account the slot-bridge saturation and the deep-bar effect, is developed. The model extensions can be plugged into a standard machine model and parametrized easily. The proposed model can be applied to time-domain simulations, real-time control, and identification. The model is validated by means of finite-element analysis and experiments using a four-pole 5.6-kW induction machine. The results show that the accuracy of the proposed model is superior to the standard model, particularly under transient excitation typically used in standstill self-commissioning tests of induction motor drives.

This article analyzes and discusses peak-current mode control (PCMC) in dc–dc voltage regulators using power inductors subjected to saturation. It is proved that the impact of inductors saturation on the operation of the PCMC regulators can be reliably predicted by means of the proposed mathematical model and technique. The results of circuit simulations and experimental measurements, regarding a dc–dc boost regulator, validate the theoretical analysis and the proposed model. The results confirm that the use of saturable inductors is a viable and reliable solution for PCMC regulators and demystify some concerns about the behavior of saturable inductors in the presence of line/load transients and overloads.

This article presents a direct power control method based on modulated model predictive control for a doubly fed induction machine. The modulated predictive control algorithm constructs an optimal voltage vector from two inverter states that give a minimum absolute error in the active and reactive power. This article focuses on the effects of magnetic saturation and its impact on the accuracy of computed reactive power when the stator current sensors are not installed. To reduce the impact of magnetic saturation on reactive power computation, the machine’s magnetizing characteristic is identified through a self-commissioning scheme introduced in this article. The identified magnetizing curve is utilized to construct a full-state stator flux observer, which is used to accurately estimate stator currents that appear in the reactive power equation. Experimental results are presented to demonstrate the accuracy of the reactive power computation in the absence of stator current sensors while conserving the rapid transient response offered by a modulated predictive control strategy for active and reactive power regulation.

This paper revisits the behavioral modeling of inductors used for Switch-Mode Power Supply (SMPS) design. A novel unified behavioral modeling for power inductors is herein proposed, which considers the DC current passing through the device and the equivalent applied voltage and switching frequency as model inputs, and the resulting peak-to-peak current ripple, total power loss and temperature as model outputs. The proposed behavioral modeling relies on simple analytical formulas, discovered from experimental measurements by using a multi-objective evolutionary algorithm. The resulting behavioral models allow to define the “Constrained Operating Area” of a power inductor, which describes the boundary area in the three-dimensional domain of switching frequency, DC current and equivalent voltage that can be applied to the component while maintaining its peak-to-peak current ripple, power loss and temperature within given limits. The experimental case studies presented in the paper eventually confirm the reliability of the proposed behavioral modeling approach and of the resulting models, in the assessment of the suitability of a given inductor and in the comparative evaluation among different inductors for a given SMPS application.

A motivação principal do trabalho foi a hipótese de que um gerador de indução, devido à sua condição mais saturada, não teria seu comportamento adequadamente descrito pelo modelo clássico, já consagrado na análise de motores em regime permanente. Após a revisão bibliográfica foi então feita então uma abordagem analítica sobre conceitos ligados a harmônicas espaciais de fmm e de condutância magnética do entreferro. Também foram feitos estudos e implementações da modelagem analítica para cálculo de resistências, reatâncias de magnetização e de dispersão para levar em conta a possível modificação de parâmetros em função de saturação. Paralelamente a isto foram realizados ensaios de rotor bloqueado, a vazio e sob carga na condição de motor e de gerador com uma máquina comercial. Como os resultados das simulações apresentavam diferenças significativas com relação àqueles obtidos nos ensaios, principalmente na condição de escorregamento negativo, buscou-se na análise da máquina pelo método dos elementos finitos alguma informação. Apesar das informações obtidas serem relevantes elas não ajudaram a minimizar as diferenças entre ensaio e modelagem. O que mais conduziu à conclusão do estudo foi a consideração da variação da reatância de magnetização com a tensão de entreferro e da variação da reatância de dispersão da ranhura do rotor usando a abordagem das ranhuras fechadas com saturação da ponte da ranhura. Estas considerações, juntadas ao cálculo analítico das perdas suplementares e das correntes interbarras levaram ao modelo proposto final. As simulações e os ensaios no laboratório mostraram que o modelo proposto produz resultados mais confiáveis do que os obtidos pelo modelo clássico, na condição de motor e de gerador, confirmando a hipótese inicial. O modelo então, buscado inicialmente para o gerador, estendeu-se também para o funcionamento como motor onde apresentou ótimos resultados. The main motivation of the work was the hypothesis that an induction generator, due to its more saturated condition, would not have its behavior adequately described by the classic model, already enshrined in the analysis of motors in steady state. After the bibliographic review, an analytical approach was then made on concepts related to spatial harmonics of mmf and magnetic conductance of the air gap. Studies and implementations of analytical modeling were also carried out to calculate resistances, magnetization, and dispersion reactances to take into account the possible modification of parameters due to saturation. In parallel to this, tests were performed on locked rotor, at no-load and under load in the condition of motor and generator with a commercial machine. As the results of the simulations presented significant differences in relation to those obtained in the tests, mainly in the condition of negative slip, we sought in the analysis of the machine by the finite element method some information. Although the information obtained is relevant, it did not help to minimize the differences between testing and modeling. What most led to the conclusion of the study was the consideration of the variation of the magnetization reactance with the air gap voltage and of the variation of the dispersion reactance of the rotor slot using the closed slot approach with saturation of the slot bridge. These considerations, coupled with the analytical calculation of supplementary losses and interbar currents, led to the final proposed model. The simulations and tests in the laboratory showed that the proposed model produces more reliable results than those obtained by the classic model, in the condition of motor and generator, confirming the initial hypothesis. The model, initially sought for the generator, was extended to the operation as a motor where it presented excellent results.

More compact Switch-Mode Power Supplies (SMPSs) satisfying typical design specifications can be obtained by exploiting ferrite core inductors working in partial saturation. In this case, the inductance is no longer a constant parameter, since it exhibits a sharp drop as the inductor current increases. A behavioral model was recently proposed, which provides the inductance at steady state as a function of easy-to-measure quantities. Here, a generalization of this model is presented, in order to capture the inductance behavior also during thermal transients. The model fitting to experimental measurements relies on an iterative optimization procedure grounding on accurate SMPS simulations based on shooting analysis. The model validation exploits the envelope analysis method, particularly suitable for slow-fast systems. The obtained fitting results show a good agreement with experimental data both in transient conditions (after sudden variation of the SMPS operating condition) and at steady state. Finally, by partially re-identifying the model based on data measured when the inductor is cooled with a fan, we still obtain a good matching between model and experimental data.

The purpose. Paper purpose is working out of a technique of the solution of nonlinear problems in an analytic form, namely a piecewise linear approximation of magnetization curve of a magnetic circuit by discontinuous functions, and the solution of the nonlinear differential equation for an electric circuit which contains this type of device. For an example of use of a technique the approximate calculation of the peak-transformer working in a regime of saturation of a magnetic circuit is resulted. Methodology. By working out of a technique of piecewise linear approximation in the capacity of the basic mathematical apparatus individual discontinuous functions were used. Calculation of a nonlinear problem for a current finding in the transformer was analogous to a nonlinear problem for magnetic field strength finding in a ferromagnetic. Results. The design procedure of currents and voltage of the transformer working in a regime of saturation, on the basis of analytical record of a piecewise linear approximation of magnetization curve of a magnetic circuit is developed. Originality. For the first time with reference to the characteristic of magnetization of the peak-transformer the method of piecewise linear approximation is applied. Practical value. The offered technique can be directly used for electromagnetic calculation of peak - transformer as a part of the general (operated) electrotechnical device at a design stage and optimization., Цель. Целью статьи является разработка методики применения аналитической записи кусочно-линейной аппроксимации кривой намагничивания для расчета нелинейной электрической цепи, содержащей трансформатор, работающий в режиме насыщения магнитопровода. Методика. При разработке методики кусочно-линейная аппроксимация и нелинейное дифференциальное уравнение электрической цепи записывались с использованием единичных разрывных функций. Расчет нелинейной задачи для нахождения тока в трансформаторе был аналогичен нелинейной задаче для определения напряженности магнитного поля в ферромагнетике с кусочно-линейной аппроксимацией кривой намагничивания. Результаты. Разработана методика расчета токов и напряжений трансформатора, работающего в режиме насыщения, на основе аналитической записи кусочно-линейной аппроксимации кривой намагничивания магнитопровода. Научная новизна. Впервые применительно к характеристике намагничивания пик-трансформатора использована аналитическая запись кусочно-линейной аппроксимации. Практическое значение. Предлагаемая методика может быть непосредственно использована для электромагнитного расчета вариантов пик – трансформатора в составе общего (управляемого) электротехнического устройства на стадии проектирования и оптимизации., Мета. Метою статті є розробка методики застосування аналітичного запису кусочно-лінійної апроксимації кривої намагнічування для розрахунків нелінійного електричного кола, що містить трансформатор, який працює в режимі насичення магнітопроводу. Методика. При розробці методики кусочно-лінійна апроксимація й нелінійне диференціальне рівняння електричного кола записувалося з використанням одиничних розривних функцій. Розрахунки нелінійної задачі для пошуку струму в трансформаторі були аналогічні нелінійній задачі для визначення напруженості магнітного поля у феромагнетику с кусочно-лінійною апроксимацією кривої намагнічування. Результати. Розроблена методика розрахунків струмів і напруг трансформатора, що працює в режимі насичення, на основі аналітичного запису кусочно-лінійної апроксимації кривої намагнічування магнітопроводу. Наукова новизна. Уперше стосовно до характеристики намагнічування пік-трансформатора використано аналітичний запис кусочно-лінійної апроксимації Практичне значення. Запропонована методика може бути безпосередньо використана для електромагнітних розрахунків варіантів пік – трансформатора в складі загального (керованого) електротехнічного пристрою на стадії проектування й оптимізації.

This paper proposes a nonlinear controller based on feedback linearization for Synchronous Reluctance Motors (SynRM) drives that takes into consideration the self and cross-saturation effects. Such control technique permits the dynamics of both the speed and flux loops to be maintained constant independently from the load and the saturation of the iron core. The proposed technique has been tested experimentally on a suitably developed test set-up.

Употреба електричних машина у електричним возилима и у електромоторним погонима великих снага често се базира на концепту вишефазних машина и претварача. Предмет научне расправе у оквиру дисертације је разматрање, утврђивање и уважавање електромагнетских појава које се јављају у току рада ових машина, а које могу утицати на одабир оптималне топологије статорског намотаја. Постоји потреба за анализом појава које се јављају при раду вишефазне машине, а које утичу на промене њених параметара и перформанси, што је искоришћено као темељ за формирање методологије пројектовања статорског намотаја шестофазне машине. Док су адекватни математички модели вишефазних машина за линеарне услове рада доступни, то није случај са моделима код којих је присутно засићење магнетског кола. У овој дисертацији обрађена је проблематика пројектовања намотаја статора на примеру шестофазне машине. Анализирана је појава засићења магнетског кола при различитим условима напајања, при чему се анализира потенцијална употреба постојећих модела засићених трофазних машина за потребе моделовања засићених вишефазних машина. Код модела шестофазне машине са векторски распрегнутим равнима анализирано је постојање међусобног утицаја између различитих равни при појави засићења магнетског кола, а што је од значаја за развој прецизнијих модела и алгоритама управљања. Дисертација се ослања на аналитичка разматрања, анализу применом методе коначних елемената и експерименталне резултате. Показано је да на засићење на путу главног флукса утичу компоненте струје које не доприносе стварању електромеханичког момента, тј. установљено је постојање међураванског унакрсног засићења, што доводи до потребе за развојем нових модела шестофазних и осталих вишефазних машина, који ће уважити овај ефекат. Поред засићења, анализиране су различите топологије статорских намотаја ради остваривања бољих перформанси шестофазне машине са становишта смањења површинских губитака у ротору. Установљено је да скраћење навојног корака намотаја често не доводи до смањења ових губитака. Као резултат анализе формирана је методологија оптималног пројектовања статорског намотаја шестофазне машине која се базира на основним научним доприносима ове дисертације. The use of electrical machines in electric vehicles and high-power drives frequently requires multiphase machines and multiphase inverters. The topic of the scientific discussion within the dissertation is the consideration, determination and appreciation of the electromagnetic phenomena that occur during the operation of multiphase machines, which can be related to the selection of the optimal topology of the stator winding. There is a need to analyze these phenomena, which influence the changes in parameters and performances. While appropriate mathematical models under the linear magnetic conditions are readily available for multiphase machines, the same cannot be said for the models of the saturated multiphase machines. This dissertation examines the saturation in an asymmetrical six-phase induction machine under different supply conditions and the possibility of extending the existing linear models to the saturated case. Specifically, in the vector space decomposed model, the mutual coupling between sequence planes is analyzed under saturated conditions, which is important for modeling and control purposes. The dissertation relies on analytical considerations, finite element analysis and experimental results. It is shown that the saturation of the main flux path is influenced by the current components in the orthogonal (non-fundamental) sequence plane. The existence of the cross-coupling effects between different subspaces is recognized, thus implies the need to develop new multiphase machine models which take this effect into account. In addition, various stator winding topologies have been analyzed in order to achieve better performance of the six-phase AC machine. An analysis of the different stator winding topologies and their influence on harmonic losses in the rotor cage, was presented. It has been found that the shortening of the winding pitch often has no effect on reducing these losses. The methodology of designing the stator winding of a six-phase machine is presented, which takes into account the contributions presented in the dissertation. A closer study of the dissertation research is the analysis of the phenomena which are significant in the design and optimization procedure when constructing a sixphase AC machine. The dissertation describes the phenomena that occur during characteristic operating regimes and are of importance during the design process. Therein, the magnetic circuit saturation effect was analyzed in greatest detail, while considering the existing methods for modeling in both three-phase and six-phase machines. It was concluded that the frequency dependence of parameters is present as in three-phase machines.

The purpose of this article is to develop a method and algorithm for the calculation of the steady-state mode and static characteristics of the squirrel-cage asynchronous motors that are supplied by a three-phase network with an asymmetrical voltage system. The aim is achieved by developing a method where the mathematical model of the motor takes into account the saturation of the magnetic core and the current displacement in the short-circuited rotor bars. Magnetization characteristics of the main magnetic flux and the leakage fluxes paths are used to account for the saturation. To account for the current displacement in the rotor winding the bars are divided into several layers throughout the height, resulting in a number of windings on the rotor with mutual inductive couplings. In the mathematical model, the processes in the asynchronous motor are described by a system of the nonlinear differential equations of electromagnetic equilibrium, composed in the fixed three-phase coordinate axes. The solution of this system in the steady-state mode is the periodic dependence of the currents, which are determined by solving the boundary problem. For this purpose, their algebraization is carried out by approximation of the periodic dependences at the nodes’ grid of the period of repeatability of the process by the third order splines. The solution of the problem is to determine the nodal values of coordinates on the period from the obtained nonlinear system of algebraic equations. For this purpose, the continuation method and iterative refinement by the Newton method were used. Calculation of the static characteristics was performed by the differential method.

Poor modeling of air-gap is the main defect of conventional magnetic equivalent circuit (CMEC) model for performance analysis of electric machines. This paper presents an improved magnetic equivalent circuit (IMEC) which considers all components of air-gap permeance such as the mutual permeances between stator and rotor teeth, and the leakage permeances between adjacent stator teeth and adjacent rotor teeth in the air-gap. Since the conformal mapping (CM) method can accurately take into account the air-gap region, IMEC gets help from the CM method for calculating the air-gap permeance components. Therefore, the obtained model is a hybrid analytical model, which can accurately take into account the magnetic saturation in iron parts by using the CMEC, and the real paths of fringing flux, leakage flux, and the main flux in the air-gap by using the CM method. For a typical wound rotor induction motor, the accuracy of the results obtained by IMEC is verified by comparing them with the corresponding results determined through CMEC, improved conformal mapping (ICM), finite element method (FEM), and the experiment results.

This paper proposes a new generalized equivalent magnetic circuit model for the preliminary design of a toroidally-wound limited angle servo motor (LASM). In the model, the magnetic networks are formulated as a function of the pole number and geometric dimensions. Nonlinear saturation effect of the ferromagnetic material is also taken into consideration. A multi-objective optimization function involving the torque requirement, the mass, the time constant, and magnetic saturations of ferromagnetic material is introduced. Based on the proposed model, six design cases with different objectives have been carried by the particle swarm optimization (PSO) method. The comparisons of different optimization cases demonstrate the effectiveness and computation efficiency of the proposed method, and hence its suitability in preliminary design. Moreover, the generalized model can be readily applied in the other electromagnetic modelling.

Ultrasound methods are currently employed in a wide range of applications. They are integrated in complex electronics systems, like clinical echographs, but also in small and compact boards, like industrial sensors, embedded systems, and portable devices. Ultrasound waves are typically generated by energizing a piezoelectric transducer through a high-voltage sequence of small sinusoidal bursts. Moreover, in several applications, the ultrasound board should work in a wide frequency range. This makes the transmitter, i.e., the electronics that drives the transducer, a key part of the circuit. The use of a small transformer simplifies the electronics and reduces the need of high-voltage power sources. Unfortunately, the transformer magnetic core, when subjected to the sequence of bursts employed in ultrasound, is particularly prone to saturation. This phenomenon limits the maximum voltage and/or the minimum frequency the transformer can be employed for. In this work, a transmitter based on a transformer is proposed. Inspired by the technique currently employed in the power network transformers, we added a prefluxing circuit, which improves the saturation performance 2-fold. The proposed transmitter was implemented in a test board and experimented with two commercial transformers at 80 Vpp. Measurements show that the proposed prefluxing circuit moves down the minimum usable frequency 2-fold: from 400 to 200 kHz for one of the two transformers, and from 2.4 to 1.2 MHz for the other.

application/pdf, 学位論文(Thesis)

The current paper discusses the theoretically detailed physical analysis of the effects of main flux saturation in smooth air gap AC machines. For that purpose, three sections are presented. The first one deals for presenting equivalence saturation-air gap. The second presents the equivalence of inductances between saturation induction machines and a dismounted salient pole synchronous machine. The method analyzes the leakage inductances that properly represent the corresponding leakage fluxes. The third section treats the physical interpretation of the cross-saturation. It is possible to show that the equations and physical picture in a saturated smooth-air-gap machine are similar to the equations and physical picture in a non-saturated salient-pole machine, where mutual coupling exists between the direct and quadrature axes and the self-inductances are also different on the non-salient part of the machine due to the variation of the reluctance with the rotor angle.