An annoying tonal noise is produced by modern electrical trains duringacceleration and deceleration. This noise is caused by electromagneticforces generating structural vibrations, especially from the traction motors.The electromagnetic noise is dominant at low train speeds and affectsboth the passengers on the train and on platforms, as well as peopleliving near the track. The focus on this issue has increased the last years,both regarding legislation, contractual requirements and also because ofexpectations from citizens and travelers. To be able to design low noiseelectric drive systems, a thorough understanding of the cause and thepossibility to predict the electromagnetic noise is needed. This thesisdescribes the modelling and simulation of an complete multi-physicsreal-time environment for prediction and analysis of the electromagneticnoise. The simulation results are validated against measurements of thestructural vibration and acoustic response of a real traction motor fed bya power converter running in the entire operational range. / <p>QC 20161118</p>

The effect of PWM frequency modulation on power supply conducted EM! noise emission is investigated. Significant reduction of emission is possible with PWM frequency modulation scheme. A forward converter is used to verify the effectiveness of the scheme. A guidance of parameter selection for noise reduction is given. / Master of Science

La machine asynchrone est à ce jour la référence dans les moteurs de traction ferroviaire. De nombreuses contraintes dictées par des normes notamment au niveau du bruit acoustique poussent l’industrie à développer des moteurs plus silencieux. Le vrillage connu pour réduire les ondulations de couple semble apporter également une réelle solution afin de diminuer les vibrations et le bruit émis par la machine. C’est dans ce contexte que ce projet en collaboration avec Alstom-Transport situé à Ornans et le soutien de MEDEE (pôle régional sur la maitrise énergétique) est réalisé. Cette thèse se focalise plus particulièrement sur le calcul des forces électromagnétiques dans l’entrefer à l’origine des vibrations, du bruit et du couple. Des modèles analytiques et à éléments finis estimant les forces électromagnétiques et intégrant le vrillage sont présentés et confrontés à des mesures expérimentales de vibration, de bruit et de couple. Les modèles utilisés sont valables pour les machines asynchrones à cage d’écureuil mais sont facilement adaptables pour les machines synchrones. Ils permettent de comprendre l’origine des forces électromagnétiques responsables du bruit et de trouver des configurations de machines moins bruyantes en jouant sur divers paramètres tels que : le vrillage, mais aussi le nombre de paires de pôles, le nombre d’encoches au stator et au rotor, la forme des encoches, la distribution du bobinage, etc. / The induction machine is the reference in railway traction motors. Numerous constraints dictated by standards, particularly regarding acoustic noise, are driving the industry to develop quieter engines. The skewing known to reduce torque ripples seems to also provide a real solution to reduce vibration and noise emitted by the machine. In this context, the project is realized in collaboration with Alstom-Transport located in Ornans with the support of MEDEE (regional pole on energy control). This thesis focuses on the calculation of magnetic forces in the air gap which originate vibration, noise and torque. Analytical and finite element models, which estimate electromagnetic forces and integrate skewing, are presented and compared with experimental measurements of vibration, noise and torque. The models used are valid for the squirrel-cage induction machines but are easily adaptable for synchronous machines. This allows one to understand the origin of the electromagnetic forces responsible for the noise, and to find configurations of less noisy machines. Various parameters such as skewing can be modified to reach this goal, as well as the number of pole pairs, the stator and rotor teeth number, the slot shape, the winding distribution, and so on.

A dominating source for the radiated acoustic noise from a train at low speeds is the traction motor. This noise originates from electromagnetic forces acting on the structure resulting in vibrations on the surface and thus radiated noise. It is often perceived as annoying due to its tonal nature. To achieve a desirable acoustic behavior, and also to meet legal requirements, it is of great importance to thoroughly understand the generation of noise of electromagnetic origin in the motor and also to be able to control it to a low level. In this work, experimental tests have been performed on a traction motor operated from pulse width modulated (PWM) converter. A PWM converter outputs a quasi-sinusoidal voltage created from switched voltage pulses of different widths. The resulting main vibrations at PWM operation and their causes have been analyzed. It is concluded that an appropriate selection of the PWM switching frequency, that is the rate at which the voltage is switched, is a powerful tool to influence the noise of electromagnetic origin. Changing the switching frequency shifts the frequencies of the exciting electromagnetic forces. Further experimental investigations show that the trend is that the resulting sound power level decreases with increasing switching frequency and eventually the sound power level reaches an almost constant level. The underlying physical phenomena for the reduced sound power level is different for different frequency ranges. It is proposed that the traction motor, similar to a thin walled cylindrical structure, shows a constant vibration over force response above a certain frequency. This is investigated using numerical simulations of simplified models. Above this certain frequency, where the area of high modal density is dominating, the noise reducing effect of further increasing the switching frequency is limited. / <p>QC 20180109</p>

With the advent of power electronics, inverter-driven induction motor are finding increased use in industries because of applications that demand variable speed operations and because of the potential savings in energy usage. However, these drives sometimes produce unacceptably high levels in vibration and acoustic noise. A literature survey has revealed that while there has been intensive research on the design of inverters to minimize acoustic noise radiation from these drives, the vibro-acoustic behaviour of an induction motor structure has received relatively little attention. The primary objective of this research project, therefore, is to develop a general strategy/algorithm for estimating the acoustic noise radiated from inverter-driven induction motors. By using a three-phase, 2.2 kW induction motor, the vibration modes due to various structural components (such as the rotor, the stator/casing, the endshields and the base plate) of the motor structure were analysed by experimental modal testing. Results indicate that the vibration modes due to the rotor are only important at low frequencies. It has been found that the power injection method gives more accurate measurement of the damping of a motor structure than the modal testing and the time decay methods. If a point force excitation is used, then it is more accurate to measure the sound radiation efficiency than the power conversion efficiency for motor structures. The effect of three different inverter designs (an ideal ???almost sinusoidal??? controller and two commercially available PWM inverters) on the radiated acoustic power were assessed for both no-load and load conditions using sound intensity measurements conducted in an anechoic room. The results indicate that although the sound power level due to aerodynamic and mechanical noise increases at a rate of 12 dB per doubling of the motor speed, the electromagnetic noise dominates at low motor speeds and is still a significant noise source even at high motor speeds. For inverters with low switching frequencies, the radiated sound power level is almost 15 dB higher than the ideal case at low speeds and is relatively insensitive to the motor speed. For inverters that implement the random modulation technique, the change in the total sound power level with the level of the random modulation is very small but the tonal nature of the noise is greatly reduced. The vibration behaviour of a motor structure was modeled using the finite element method (FEM) and validated using the experimental modal testing results. It has been found that it is essential to model the laminated stator as an orthotropic structure. While the details of other structural components (such as the endshields, the teeth in the stator and the windings) are not so important, it is essential that they are incorporated into the structural model as simplified structures to account for their mass, stiffness and boundary conditions imposed on the motor structure. Based on this structural model, the radiated acoustic power for various operating conditions has been predicated using the boundary element (BEM) and the electromagnetic force calculated from an electromagnetic finite element model. The predicted results agree reasonably well with experimental measurements. Despite the success of the FEM/BEM approaches, they can be prohibitively expensive (in terms of computer resources required) to apply to large motors and high frequencies. Thus the feasibility of using a statistical method, namely, the statistical energy analysis (SEA), to estimate the radiated acoustic sound power from an inverter-driven induction motor has been examined. In order to carry out this analysis, analytical expressions for calculating the natural frequencies and radiation efficiency of finite length circular cylindrical shells (which are simplified models of the stator and casing of a motor structure) were firstly derived. The internal loss factors and coupling loss factors of the motor structure were determined experimentally using the power injection method. Then by introducing an equivalent surface mobility of circular cylindrical shells for the electromagnetic force, the vibration response and the acoustic noise radiated from each part of the motor structure were estimated. Results indicate that SEA method is potentially an efficient and effective tool in estimating the noise radiated from inverter-driven induction motors.

With increase in frequency and convergence toward mixed signal systems, supplying stable voltages to integrated circuits and blocking noise coupling in the systems are major problems. Electromagnetic band gap (EBG) structures have been in the limelight for power/ground noise isolation in mixed signal applications due to their capability to suppress unwanted electromagnetic mode transmission in certain frequency bands. The EBG structures have proven effective in isolating the power/ground noise in systems that use a common power supply. However, while the EBG structures have the potential to present many advantages in noise suppression applications, there is no method in the prior art that enables reliable and efficient synthesis of these EBG structures. Therefore, in this research, a novel EBG synthesis method for mixed signal applications is presented. For one-dimensional periodic structures, three new approaches such as current path approximation method, border to border radius, power loss method have been introduced and combined for synthesis. For two-dimensional EBG structures, a novel EBG synthesis method using genetic algorithm (GA) has been presented. In this method, genetic algorithm (GA) is utilized as a solution-searching technique. Synthesis procedure has been automated by combining GA with multilayer finite-difference method and dispersion diagram analysis method. As a real application for EBG structures, EBG structures have been applied to a GHz ADC load board design for power/ground noise suppression.

With the advent of power electronics, inverter-driven induction motor are finding increased use in industries because of applications that demand variable speed operations and because of the potential savings in energy usage. However, these drives sometimes produce unacceptably high levels in vibration and acoustic noise. A literature survey has revealed that while there has been intensive research on the design of inverters to minimize acoustic noise radiation from these drives, the vibro-acoustic behaviour of an induction motor structure has received relatively little attention. The primary objective of this research project, therefore, is to develop a general strategy/algorithm for estimating the acoustic noise radiated from inverter-driven induction motors. By using a three-phase, 2.2 kW induction motor, the vibration modes due to various structural components (such as the rotor, the stator/casing, the endshields and the base plate) of the motor structure were analysed by experimental modal testing. Results indicate that the vibration modes due to the rotor are only important at low frequencies. It has been found that the power injection method gives more accurate measurement of the damping of a motor structure than the modal testing and the time decay methods. If a point force excitation is used, then it is more accurate to measure the sound radiation efficiency than the power conversion efficiency for motor structures. The effect of three different inverter designs (an ideal ???almost sinusoidal??? controller and two commercially available PWM inverters) on the radiated acoustic power were assessed for both no-load and load conditions using sound intensity measurements conducted in an anechoic room. The results indicate that although the sound power level due to aerodynamic and mechanical noise increases at a rate of 12 dB per doubling of the motor speed, the electromagnetic noise dominates at low motor speeds and is still a significant noise source even at high motor speeds. For inverters with low switching frequencies, the radiated sound power level is almost 15 dB higher than the ideal case at low speeds and is relatively insensitive to the motor speed. For inverters that implement the random modulation technique, the change in the total sound power level with the level of the random modulation is very small but the tonal nature of the noise is greatly reduced. The vibration behaviour of a motor structure was modeled using the finite element method (FEM) and validated using the experimental modal testing results. It has been found that it is essential to model the laminated stator as an orthotropic structure. While the details of other structural components (such as the endshields, the teeth in the stator and the windings) are not so important, it is essential that they are incorporated into the structural model as simplified structures to account for their mass, stiffness and boundary conditions imposed on the motor structure. Based on this structural model, the radiated acoustic power for various operating conditions has been predicated using the boundary element (BEM) and the electromagnetic force calculated from an electromagnetic finite element model. The predicted results agree reasonably well with experimental measurements. Despite the success of the FEM/BEM approaches, they can be prohibitively expensive (in terms of computer resources required) to apply to large motors and high frequencies. Thus the feasibility of using a statistical method, namely, the statistical energy analysis (SEA), to estimate the radiated acoustic sound power from an inverter-driven induction motor has been examined. In order to carry out this analysis, analytical expressions for calculating the natural frequencies and radiation efficiency of finite length circular cylindrical shells (which are simplified models of the stator and casing of a motor structure) were firstly derived. The internal loss factors and coupling loss factors of the motor structure were determined experimentally using the power injection method. Then by introducing an equivalent surface mobility of circular cylindrical shells for the electromagnetic force, the vibration response and the acoustic noise radiated from each part of the motor structure were estimated. Results indicate that SEA method is potentially an efficient and effective tool in estimating the noise radiated from inverter-driven induction motors.

Voltage source inverter (VSI) fed induction motors are increasingly used in industrial and transportation applications as variable speed drives. However, VSIs generate non-sinusoidal voltages and hence result in harmonic distortion in motor current, motor heating, torque pulsations and increased acoustic noise. Most of these undesirable effects can be reduced by increasing the switching frequency of the inverter. This is not necessarily true for acoustic noise. Acoustic noise does not decrease monotonically with increase in switching frequency since the noise emitted depends on the proximity of harmonic frequencies to the motor resonant frequencies. Also there are practical limitations on the inverter switching frequency on account of device rating and losses. The switching frequency of many inverters often falls in the range 2 kHz - 6 kHz where the human ear is highly sensitive. Hence, the acoustic noise emission from the motor drive is of utmost important. Further, the acoustic noise emitted by the motor drive is known to depend on the waveform quality of the voltage applied. Hence, the acoustic performance varies with the pulse width modulation (PWM) technique used to modulate the inverter, even at the same modulation index. Therefore a comprehensive study on the acoustic noise aspects of induction motor drive is required. The acoustic noise study of the motor drive poses multifaceted challenges. A simple motor model is sufficient for calculation of total harmonic distortion (THD). A more detailed model is required for torque pulsation studies. But the motor acoustic noise is affected by many other factors such as stator winding distribution, space harmonics, geometry of stator and rotor slots, motor irregularities, structural issues controlling the resonant frequency and environmental factors. Hence an accurate model for acoustic noise would have to be very detailed and would span different domains such as electromagnetic fields, structural engineering, vibration and acoustics. Motor designers employ such detailed models along with details of the materials used and geometry to predict the acoustic noise that would be emitted by a motor and also to design a low-noise motor. However such detailed motor model for acoustic noise purposes and the necessary material and constructional details of the motor are usually not available to the user. Also, certain factors influencing the acoustic noise change due to wear and tear during the operational life of the motor. Hence this thesis takes up an experimental approach to study the acoustic noise performance of an inverter-fed induction motor at any stage of its operating life. A 10 kVA insulated gate bipolar transistor (IGBT) based inverter is built to feed the induction motor; a 6 kW and 2.3 kW induction motors are used as experimental motors. A low-cost acoustic noise measurement system is also developed as per relevant standards for measurement and spectral analysis of the acoustic noise emitted. For each PWM scheme, the current and acoustic noise measurements are carried out extensively at different carrier frequencies over a range of fundamental frequencies. The main cause of acoustic noise of electromagnetic origin is the stator core vibration, which is caused by the interaction of air-gap fluxes produced by fundamental current and harmonic currents. In this thesis, an experimental procedure is suggested for the acoustic noise characterization of an induction motor inclusive of determination of resonant frequencies. Further, based on current and acoustic noise measurements, a vibration model is proposed for the stator structure. This model is used to predict the acoustic noise pertaining to time harmonic currents with reasonable accuracy. Literature on motor acoustic noise mainly focuses on sinusoidal PWM (SPWM), conventional space vector PWM (CSVPWM) and random PWM (RPWM). In this thesis, acoustic noise pertaining to two bus-clamping PWM (BCPWM) schemes and an advanced bus-clamping PWM (ABCPWM) scheme is investigated. BCPWM schemes are mainly used to reduce the switching loss of the inverter by clamping any of the three phases to DC rail for 120◦ duration of the fundamental cycle. Experimental results show that these BCPWM schemes reduce the amplitude of the tonal component of noise at the carrier frequency, compared to CSVPWM. Experimental results with ABCPWM show that the overall acoustic noise produced by the motor drive is reduced at low and medium speeds if the switching frequency is above 3 kHz. Certain spread in the frequency spectrum of noise is also seen with both BCPWM and ABCPWM. To spread the acoustic noise spectrum further, many variable-frequency PWM schemes have been suggested by researchers. But these schemes, by and large, increase the current total harmonic distortion (THD) compared to CSVPWM. Thus, a novel variable-frequency PWM (VFPWM) method is proposed, which offers reduced current THD in addition to uniformly spread noise spectrum. Experimental results also show spread in the acoustic noise spectrum and reduction in the dominant noise components with the proposed VFPWM. Also, the current THD is reduced at high speeds of the motor drive with the proposed method.

Cette thèse porte sur la conception silencieuse par démarches inverses de machines synchrones à aimants permanents dotées de bobinages dentaires. Notre travail se focalise sur l’analyse des raies de forces radiales à l’origine du bruit magnétique. En premier lieu, un modèle direct électromagnétique, nous a permis de déterminer le spectre spatio-temporel de la force radiale dans l’entrefer. Ce dernier nous offre la possibilité d’obtenir pas à pas et de manière analytique l’induction radiale dans l’entrefer, résultat du produit de la force magnétomotrice totale et de la perméance d’entrefer globale. Plusieurs machines dotées d’un bobinage dentaire et distribué ont été évaluées, comparées à des simulations par éléments finis et corroborés par une analyse modale opérationnelle sur un prototype existant au laboratoire. Puis la démarche inverse de conception est abordée par le biais de deux outils « analytiques prédictifs » donnant les origines des ordres faibles spatio-temporels de la force radiale dans l’entrefer. Enfin, la résolution du problème inverse est conduite au moyen d’une boucle itérative d’optimisation donnant parmi un échantillon de solutions, une fonction de bobinage, visant à atténuer ou supprimer une raie potentiellement risquée en termes de nuisances acoustiques / This thesis deals the quiet design by inverses approaches of synchronous machines with permanent magnets concentrated windings. Our work focuses on the analysis of magnetic noise origin of air gap radial force orders. Firstly a direct electromagnetic model allowed us to determine the spatio-temporal spectrum of air gap radial pressure. The latter offers us the possibility of obtaining step by step and in an analytical way the radial induction in the gap, result of the product of the total magnetomotive force and global air gap permeance. Several machines equipped with a concentrated winding and distributed were evaluated, compared to simulations by finite elements and corroborated by an operational deflection shape on an existing prototype in the laboratory. In the second time two inverse approaches named predictive methodology identified the radial pressure low order origin. Finally, the resolution of the inverse problem is carried out by means of an iterative optimization loop giving among a sample of solutions, a winding function, aimed at attenuating or eliminating a potential risky line in terms of acoustic nuisances.

Afin de définir une conception optimale d’un système électromécanique, celui-ci doit intégrer des contraintes toujours plus drastiques et de nombreux phénomènes physiques issus de : l’électromagnétique, l’aérothermique, l’électronique, la mécanique et l’acoustique. L’originalité de cette thèse est de proposer une modélisation multi-physique pour la conception reposant sur des modèles à constantes localisées : solution intermédiaire entre la modélisation analytique et numérique. Ces différents modèles permettront l’étude et la conception sous contraintes d’une machine synchrone à aimants permanents dédiée pour la traction ferroviaire. Les résultats de simulations seront comparés à des résultats éléments finis mais aussi à des essais expérimentaux. Ce modèle multi-physique est entièrement paramétré afin d’être associé à des outils d’optimisation. On utilisera ici une optimisation par essaim de particules pour chercher des compromis entre différents objectifs sous forme de Front de Pareto. Dans ce papier, nous ciblerons les objectifs suivants : le couple d’origine électromagnétique et le bruit d’origine électromagnétique. Finalement une étude de sensibilité valide la robustesse de la conception retenue quand celle-ci est soumise aux contraintes de fabrication. L’objectif étant de poser les bases d’un outil d’aide à la décision pour le choix d’une machine électrique / In order to perform an optimal design of electromechanical system, the designer must take into account ever more stringent constraints and many physical phenomena from electric, magnetic, aeraulic, thermic, electronic, mechanic and acoustic. The originality of this thesis is to put forward a multi-physic design based on lumped models: halfway between analytical and numerical modeling. These models allow sizing a permanent magnet synchronous machine under constraints for rail traction. The results are validated with finite element simulations and experimental analysis. The multi-physic modeling is fully automated, parameterized, in order to combine the model with the optimization tool. We used here particle swarm optimization to search compromises between several objectives (Pareto Front). In this paper, we focus on electromagnetic torque and electromagnetic noise. Finally a sensitive study validates the robustness of selected design when it is subjected to manufacturing constraints. The aim of this work is to propose a decision tool to size electrical machines