The main purpose of this thesis is to utilize transformer oil dissolved gas for abnormal conditions diagnose. The thesis also develops an analysis method which based on three different existing theories to obtain fast and accurate new diagnosis procedures. The procedure by using transformer oil dissolved gas can define the types and locations of transformer abnormal parts. The sample oil from an on-line transformer can give variable and useful data which can be analyzed the total amount of flammable gas in the laboratory. The type of faults of transformer can be diagnosed easily from the data. Also the over-heat uncovered metal parts of the transformer can be identified. Furthermore, the displacement of silicon sheet core caused by vibration can be obtained after disassembling the transformer. This displacement will cause over-heating phenomenon due to eddy current circulation. After improvement of silicon steel structure, the over-heating phenomenon is disappear and the amount of sample oil dissolved gas keep almost constant. The method which is proposed in the thesis improves the fault identification significantly. A practical transformer rated at 336 MVA combined by three single 23.75kV/345kV transformers have been selected to support the diagnosis program. Periodic collecting sample oil and analysis the total quantity of dissolved gas can diagnose abnormal conditions primarily. The diagnosis program can identify the types and locations of the faults with the diagnosis information. The transformer then can be stripped down for repair and maintenance. The diagnosis analysis program from the dissolved gas can identify the transformer faults efficiently. The data also can make right decision whether the transformer operating normally or not. To obtain the best maintenance conditions, periodic collecting oil sample and carrying on the analysis in the laboratory is most efficiently method. The method which proposed in the thesis can offer the best maintenance data to secure the transformer operating reliability and safety.

A device was developed to directly measure skin friction on an external test plate in transonic flight conditions. The tests would take place on the FTF-II flight test plate mounted underneath a NASA F-15 aircraft flying at altitudes ranging from 15,000 to 45,000 ft. at Mach numbers ranging from 0.70 to 0.99. These conditions lead to predicted shear levels ranging from 0.3 to 1.5 psf. The gage consisted of a floating element cantilevered beam configuration that was mounted into the surface of the test plate in a manner non-intrusive to the flow it was measuring. Strain gages mounted at the base of the beam measured the small strains that were generated from the shear forces of the flow. A non-nulling configuration was designed such that the deflection of the floating head due to the shear force from the flow was negligible. Due to the large vibration levels of up to 8 grms that the gage would experience during transonic flight, a vibration damping mechanism needed to be implemented. Viscous damping had been used in previous attempts to passively dampen the vibrations of skin friction gages in other applications, yet viscous damping proved to be an undesirable solution due to its leakage problems and maintenance issues. Three methods of damping the gage without a fluid filled damper were tested. Each gage was built of aluminum in order to maintain constant material properties with the test plate. The first prototype used a small internal gap and damping properties of air to reduce the vibration levels. This damping method proved to be too weak. The second prototype utilized eddy current damping from permanent magnets to dampen the motion of the gage. This mechanism provided better damping then the first prototype, yet greater damping was desired. The third method utilized eddy current damping from an electromagnet to dampen the motion of the gage. The eddy current damper achieved a much larger reduction in the vibration characteristics of the gage than the previous designs. In addition, the gage was capable of operating at various levels of damping. A maximum peak amplitude reduction of 33 % was calculated, which was less than theoretical predictions. The damping results from the electromagnetic gage provided an adequate level of damping for wind tunnel tests, yet increased levels of damping need to be pursued to improve the skin friction measurement capabilities of these gages in environments with extremely high levels of vibration. The damping provided by the electromagnet decreased the deflections of the head during 8 grms and 2 grms random noise vibrations bench tests. This allowed for a greater survivability of the gage. In addition, the reduction of the peak amplitude provided output with vibration induced noise levels ranging from 24 % to 5.9 % of the desired output of the gage. The gage was tested in a supersonic wind tunnel at shear levels of tw=3.9 to 5.3 psf. The shear levels encountered during wind tunnel verification tests were slightly larger than the shear levels encountered on the F-15 flight test plate during the flight tests, but the wind tunnel shear levels were considered adequate for verification purposes. The experimentally determined shear level results compared well with theoretical calculations / Master of Science

Electromagnetic Acoustic Transducers (EMATs) are advanced ultrasonic transducers that generate and detect acoustic waves in an electrically conducting material without making physical contact with the material unlike its counterpart, the piezoelectric transducers (PZT). The conventional EMAT consists of copper coil that generates the dynamic field when excited with a sinusoidal current, a permanent or electromagnet that provides the bias field and the conducting material specimen. The complex interaction between the bias field and the Eddy current induced within the skin depth of the conducting material by the dynamic field gives rise to the acoustic wave that then propagates within the surface of the material. Within the research a finite element EMAT model was developed using commercial software Comsol Multiphysics, to study and compare the Eddy current density and Lorentz force density generated by three EMAT configurations: The Meander-line, Spiral and Key Type EMAT configuration respectively. It was observed that apart from the ease of fabrication and simplicity of connectivity when stacked in layers, the Key Type coil EMAT showed a high tendency to generate higher amplitude of Eddy current and Lorentz force test materials especially when stacked in layers. Also, the effect of varying some key EMAT parameters was investigated to determine the optimal performance of Key Type EMAT configuration on CS70 pipe steel plate. The research further developed a coupled finite element model using the same software, Comsol Multiphysics to account for the generation, propagation and detection of acoustic wave by the Key Type EMAT configuration on CS70 grade of pipe steel. The model can solve the magnetostatic, electrodynamic and elastic equations that give rise to acoustic wave generation, propagation and detection on the test material. The developed coupled finite element model was validated both analytically and experimentally to establish the validity of the finite element model. The analytical and experimental results obtained were consistent with the numerical result with an average discrepancy less than 9 % percent. Finally, the research developed a novel modelling strategy to decouple and quantify the various transduction forces in operation when normally-biased EMAT and magnetostrictive EMAT configurations are used on various grades of pipe steel materials. The strategy established the value of the critical excitation current beyond which acoustic wave is generated solely by the dynamic Lorentz force mechanism. The critical excitation currents when Magnetostrictive EMAT configurations are used to generate acoustic wave was found to be; 268A, 274A, 279A, 290A and 305A for CS70, L80SS, L80A, TN80Cr3 and J55 respectively. While for Normally-Biased EMAT configurations, the critical excitation current was found to be 190A, 205A, 240A, 160A and 200A respectively. This work also compared the critical excitation current of the two EMAT configurations studied and established that normally-biased EMATs are more efficient in the generation of acoustic waves than their magnetostrictive counterpart due to their lower value of critical excitation current.

Volvo Group Truck Technology has the ambition to automate parts of their routine service. Therefore a project was launched to investigate which parts of the routine that could be automated. The idea of this project is to lower the time spent on the service and also improve the working environment for the personnel. The purpose of this thesis is to develop and build a conceptional prototype for a low-cost crack detecting sensor. This thesis is a part of a larger proof of concept project which Volvo GTT runs in cooperation with Robotdalen and Robot Application Center (RAC). The work done in this thesis has been based on literature studies, interviews and company visits. The gathered knowledge and observations was translated into what would be required to fit the needs. This thesis covers different techniques that could be used to detect flaws in braking discs. However, this thesis is mostly focused on one non-destructive method technique based on induced eddy currents. Several non-destructive techniques and conceptual designs has been tested and evaluated with varying results during this project. The result of this thesis was a design that reacts to discontinuities in conductive materials, such as the grey cast iron material used in the Volvo trucks braking discs. The results are represented as a voltage drop change and can be visualized by an oscilloscope. This study shows that the method of choice has the potential to be used as a crack detecting system and that the system can be built reliable with rather cheap components. Further development should aim towards making the design even cheaper and the components should be assembled on a PCB instead of a breadboard in order to make the system less sensitive to noise and easier to assemble alongside the trucks braking discs.

La technique du contrôle non destructif (CND) par courants de Foucault (CF) est une solution envisageable pour caractériser l’état de contraintes dans un matériau magnétique. En effet, les propriétés magnétiques d’un matériau magnétique dépendent sensiblement de l’état de contraintes et, par ailleurs, les CF dépendent de la perméabilité magnétique. La technique des CF est potentiellement intéressante comparée à d’autres méthodes de CND, telles que la diffraction des rayons X, car elle est simple à mettre en œuvre, automatisable et peu coûteuse. Dans l'objectif de permettre in fine l’identification inverse de l’état de contraintes, un modèle prédisant l'évolution du signal fourni par un capteur à CF en fonction de l’état de contraintes du matériau ferromagnétique contrôlé a été élaboré dans cette thèse. Ceci implique la mise en place d’une double modélisation. D’une part, l’effet des contraintes sur la perméabilité magnétique a été modélisé par un modèle de comportement magnéto-élastique simplifié dérivé d'une approche multi-échelle. Cette approche permet de décrire la perméabilité magnétique d’un matériau soumis à un chargement multiaxial, en incluant notamment les effets d'anisotropie induite. D’autre part, un modèle reposant sur la méthode des éléments finis a été développé afin de prédire le signal fourni par un capteur à CF en fonction de la perméabilité anisotrope du matériau inspecté. Afin de valider la démarche de modélisation, un protocole expérimental de caractérisation magnétique et par CF a été mis en place. Les résultats de mesure obtenus présentent un bon accord qualitatif avec la modélisation, en l’absence de tout étalonnage. Une procédure d’étalonnage s'appuyant sur une mesure sous contraintes est nécessaire pour atteindre un accord quantitatif. Le modèle développé pourrait être utilisé pour concevoir des sondes à CF idoines et identifier les conditions opératoires optimales pour l'estimation de contraintes dans les matériaux magnétiques. Les procédures d'inversion à mettre en œuvre restent cependant un défi à relever / The non-destructive evaluation (NDE) technique by eddy current (EC) is a conceivable solution to characterize the stress state in magnetic materials. The approach relies on the high sensitivity of eddy current (EC) signals to the magnetic permeability, itself highly dependent on stress. The EC technique is potentially attractive compared to other NDE methods such as X-ray diffraction, due to its simple practical implementation, easiness of automation and low cost. In order to allow eventually the inverse identification of stress states in magnetic materials, a predictive model for the evolution of an EC probe signal as a function of stress has been developed during this thesis. The modelling is done in two steps. First, the effect of stress on the magnetic permeability is described using a simplified version of a multiscale model for magneto-elastic behaviour. This approach allows describing the effect of multiaxial mechanical loadings on the magnetic behaviour of materials including induced anisotropy effects. Then, the EC probe signal is determined as a function of the anisotropic permeability of the stressed material using the finite element method (FEM). In order to validate the modelling approach, an experimental setup for magnetic characterisation and EC measurements was developed. The measurements show a good qualitative accordance with the modelling results, in absence of any calibration. A calibration procedure based on a measurement under stress is necessary to obtain a quantitative agreement. The proposed model can be used to design efficient EC probes and to define optimal operating conditions to evaluate stress in magnetic materials. The development of inversion procedures, however, remains a challenge.

Road and rail vehicles and aircraft rely mainly or solely on friction brakes. These brakes pose several problems, especially in hybrid vehicles: significant wear, fading, complex and slow actuation, lack of fail-safe features, increased fuel consumption due to power assistance, and requirement for anti-lock controls. To solve these problems, a contactless magnetic brake has been developed. This concept includes a novel flux-shunting structure to control the excitation flux generated by permanent magnets. This brake is wear-free, less-sensitive to temperature than friction brakes, has fast and simple actuation, and has a reduced sensitivity to wheel-lock. The present dissertation includes an introduction to friction braking, a theory of eddy-current braking, analytical and numerical models of the eddy-current brake, its excitation and power generation, record of experimental validation, investigation and simulation of the integration of the brake in conventional and hybrid vehicles.

Vehicle suspension systems have been extensively explored in the past decades, contributing to ride comfort, handling and safety improvements. The new generation of powertrain and propulsion systems, as a new trend in modern vehicles, poses significant challenges to suspension system design. Consequently, novel suspension concepts are required, not only to improve the vehicle’s dynamic performance, but also to enhance the fuel economy by utilizing regeneration functions. However, the development of new-generation suspension systems necessitates advanced suspension components, such as springs and dampers. This Ph.D. thesis, on the development of hybrid electromagnetic dampers is an Ontario Centres of Excellence (OCE) collaborative project sponsored by Mechworks Systems Inc. The ultimate goal of this project is to conduct feasibility study of the development of electromagnetic dampers for automotive suspension system applications. With new improvements in power electronics and magnetic materials, electromagnetic dampers are forging the way as a new technology in vibration isolation systems such as vehicle suspension systems. The use of electromagnetic dampers in active vehicle suspension systems has drawn considerable attention in the recent years, attributed to the fact that active suspension systems have superior performance in terms of ride comfort and road-handling performances compared to their passive and semi-active counterparts in automotive applications. As a response to the expanding demand for superior vehicle suspension systems, this thesis describes the design and development of a new electromagnetic damper as a customized linear permanent magnet actuator to be used in active suspension systems. The proposed electromagnetic damper has energy harvesting capability. Unlike commercial passive/semi-active dampers that convert the vibration kinetic energy into heat, the dissipated energy in electromagnetic dampers can be regenerated as useful electrical energy. Electromagnetic dampers are used in active suspension systems, where the damping coefficient is controlled rapidly and reliably through electrical manipulations. Although demonstrating superb performance, active suspensions still have some issues that must be overcome. They have high energy consumption, weight, and cost, and are not fail-safe in case of a power break-down. Since the introduction of the electromagnetic dampers, the challenge was to address these drawbacks. Hybrid electromagnetic dampers, which are proposed in this Ph.D. thesis, are potential solutions to high weight, high cost, and fail-safety issues of an active suspension system. The hybrid electromagnetic damper utilizes the high performance of an active electromagnetic damper with the reliability of passive dampers in a single package, offering a fail-safe damper while decreasing weight and cost. Two hybrid damper designs are proposed in this thesis. The first one operates based on hydraulic damping as a source of passive damping, while the second design employs the eddy current damping effect to provide the passive damping part of the system. It is demonstrated that the introduction of the passive damping can reduce power consumption and weight in an active automotive suspension system. The ultimate objective of this thesis is to employ existing suspension system and damper design knowledge together with new ideas from electromagnetic theories to develop new electromagnetic dampers. At the same time, the development of eddy current dampers, as a potential source for passive damping element in the final hybrid design, is considered and thoroughly studied. For the very first time, the eddy current damping effect is introduced for the automotive suspension applications. The eddy current passive damper, as a stand-alone unit, is designed, modeled, fabricated and successfully tested. The feasibility of using passive eddy current dampers for automotive suspension applications is also studied. The structure of new passive eddy current dampers is straightforward, requiring no external power supply or any other electronic devices. Proposed novel eddy current dampers are oil-free and non-contact, offering high reliability and durability with their simplified design. To achieve the defined goals, analytical modeling, numerical simulations, and lab-based experiments are conducted. A number of experimental test-beds are prepared for various experimental analyses on the fabricated prototypes as well as off-the-shelf dampers. Various prototypes, such as eddy current and electromagnetic dampers, are manufactured, and tested in frequency/time domains for verification of the derived analytical and numerical models, and for proof of concept. In addition, fluid and heat transfer analyses are done during the process of the feasibility study to ensure the durability and practical viability of the proposed hybrid electromagnetic dampers. The presented study is only a small portion of the growing research in this area, and it is hoped that the results obtained here will lead to the realization of a safer and more superior automotive suspension system.

Vehicle suspension systems have been extensively explored in the past decades, contributing to ride comfort, handling and safety improvements. The new generation of powertrain and propulsion systems, as a new trend in modern vehicles, poses significant challenges to suspension system design. Consequently, novel suspension concepts are required, not only to improve the vehicle’s dynamic performance, but also to enhance the fuel economy by utilizing regeneration functions. However, the development of new-generation suspension systems necessitates advanced suspension components, such as springs and dampers. This Ph.D. thesis, on the development of hybrid electromagnetic dampers is an Ontario Centres of Excellence (OCE) collaborative project sponsored by Mechworks Systems Inc. The ultimate goal of this project is to conduct feasibility study of the development of electromagnetic dampers for automotive suspension system applications. With new improvements in power electronics and magnetic materials, electromagnetic dampers are forging the way as a new technology in vibration isolation systems such as vehicle suspension systems. The use of electromagnetic dampers in active vehicle suspension systems has drawn considerable attention in the recent years, attributed to the fact that active suspension systems have superior performance in terms of ride comfort and road-handling performances compared to their passive and semi-active counterparts in automotive applications. As a response to the expanding demand for superior vehicle suspension systems, this thesis describes the design and development of a new electromagnetic damper as a customized linear permanent magnet actuator to be used in active suspension systems. The proposed electromagnetic damper has energy harvesting capability. Unlike commercial passive/semi-active dampers that convert the vibration kinetic energy into heat, the dissipated energy in electromagnetic dampers can be regenerated as useful electrical energy. Electromagnetic dampers are used in active suspension systems, where the damping coefficient is controlled rapidly and reliably through electrical manipulations. Although demonstrating superb performance, active suspensions still have some issues that must be overcome. They have high energy consumption, weight, and cost, and are not fail-safe in case of a power break-down. Since the introduction of the electromagnetic dampers, the challenge was to address these drawbacks. Hybrid electromagnetic dampers, which are proposed in this Ph.D. thesis, are potential solutions to high weight, high cost, and fail-safety issues of an active suspension system. The hybrid electromagnetic damper utilizes the high performance of an active electromagnetic damper with the reliability of passive dampers in a single package, offering a fail-safe damper while decreasing weight and cost. Two hybrid damper designs are proposed in this thesis. The first one operates based on hydraulic damping as a source of passive damping, while the second design employs the eddy current damping effect to provide the passive damping part of the system. It is demonstrated that the introduction of the passive damping can reduce power consumption and weight in an active automotive suspension system. The ultimate objective of this thesis is to employ existing suspension system and damper design knowledge together with new ideas from electromagnetic theories to develop new electromagnetic dampers. At the same time, the development of eddy current dampers, as a potential source for passive damping element in the final hybrid design, is considered and thoroughly studied. For the very first time, the eddy current damping effect is introduced for the automotive suspension applications. The eddy current passive damper, as a stand-alone unit, is designed, modeled, fabricated and successfully tested. The feasibility of using passive eddy current dampers for automotive suspension applications is also studied. The structure of new passive eddy current dampers is straightforward, requiring no external power supply or any other electronic devices. Proposed novel eddy current dampers are oil-free and non-contact, offering high reliability and durability with their simplified design. To achieve the defined goals, analytical modeling, numerical simulations, and lab-based experiments are conducted. A number of experimental test-beds are prepared for various experimental analyses on the fabricated prototypes as well as off-the-shelf dampers. Various prototypes, such as eddy current and electromagnetic dampers, are manufactured, and tested in frequency/time domains for verification of the derived analytical and numerical models, and for proof of concept. In addition, fluid and heat transfer analyses are done during the process of the feasibility study to ensure the durability and practical viability of the proposed hybrid electromagnetic dampers. The presented study is only a small portion of the growing research in this area, and it is hoped that the results obtained here will lead to the realization of a safer and more superior automotive suspension system.

Phased array coils are composed of several surface coils receiving individual element signals simultaneously. Each individual surface coil provides the equivalent of the coil diameter range, and higher SNR. Therefore, combining these non-interactive phased array coils, can achieve a wide range of scan areas, uniform sensitivity and better SNR. Therefore our experiment was performed with two different coils of quadrature coil and phased array coil. Phased array MRS data were compared using various combination approaches. Data acquired by quadrature coil was regarded as a standard to verify the reliability and accuracy of metabolite concentration. The aim of our study is to do eddy current correction before and after the combination of each element coil data with LCModel analysis for quantitative comparison of metabolite concentrations. Our result shows that doing eddy current correction for each phased array coil before signal combination can achieve higher reliability and accuracy of SNR and quantitative concentrations of MR spectra in vivo.

Road and rail vehicles and aircraft rely mainly or solely on friction brakes. These brakes pose several problems, especially in hybrid vehicles: significant wear, fading, complex and slow actuation, lack of fail-safe features, increased fuel consumption due to power assistance, and requirement for anti-lock controls. To solve these problems, a contactless magnetic brake has been developed. This concept includes a novel flux-shunting structure to control the excitation flux generated by permanent magnets. This brake is wear-free, less-sensitive to temperature than friction brakes, has fast and simple actuation, and has a reduced sensitivity to wheel-lock. The present dissertation includes an introduction to friction braking, a theory of eddy-current braking, analytical and numerical models of the eddy-current brake, its excitation and power generation, record of experimental validation, investigation and simulation of the integration of the brake in conventional and hybrid vehicles.