Conventionally, system simulations of induction motor drives use lumped parameters model of the motor. This approach assumes motor parameters to be constant during the entire operation of the drive. Unfortunately, these are known to vary significantly over the operating range of the motor due to factors such as magnetic saturation, skin effects, and operating temperature. The variations in motor parameters affect motor output and control parameters resulting in degraded drive performance. One way of overcoming this problem is by coupling the field model of the induction motor with the drive simulation. By replacing the lumped parameters model with the field model, the influence of different operating conditions on motor parameters can be taken into account dynamically. In this thesis such an approach is investigated by coupling the finite element analysis of an induction motor with the system simulation of the field oriented controlled drive. The results obtained for the coupled simulation are promising and possible future works to make this method of simulation more accurate and reliable are recommended.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Includes bibliographical references (p. 170-177).

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Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 198-201). Also available on the Internet.

Induction motors are reliable and widely used in industrialised nations. However induction motors, like any other machine, will eventually fail. If the failure is not anticipated, it can result in a significant revenue loss. Therefore, there is a strong need to develop an efficient maintenance program. The most cost-effective solution is condition-based maintenance. An effective condition-based maintenance program requires an on-line condition monitoring system that can diagnose the condition of an induction motor in order to determine the types of faults and their severity while the motor is under a normal operating condition. The work in this thesis investigates the detection of stator and rotor faults (i.e. shorted turn faults, eccentricity faults, and broken rotor bar faults) using three types of sensor signals (i.e. current, leakage flux, and vibration) under different loading conditions. The work is based on an extensive series of sensor measurements taken using a number of nominally identical healthy machines (2.2 kW) and custom-modified machines (2.2 kW) with configurable stator and rotor fault settings. The thesis starts by investigating the estimation of rotor speed and rotor slot number. These two parameters are important in determining the fault frequency components that are used for detecting the stator and rotor faults. The rotor speed investigation compares four different estimation methods from the three different sensor signal types. It is found that the speed estimation techniques based on the eccentricity harmonics and the rotor frequency in the stator current, the axial leakage flux, and the motor vibration sensor signals can detect the rotor speed very accurately even when the load is as low as 2%. Similarly, this thesis proposes three different rotor slot number estimation techniques from the three different types of sensors and demonstrates that all three techniques can estimate the rotor slot number accurately. In addition, it is shown that the reliability of the estimation techniques can be increased significantly when the three techniques are combined. The shorted turn investigation in this thesis examines and compares potential shorted turn features in the three sensor signal types under five different fault severities and ten different loading conditions. The useful shorted turn features are identified in the thesis, and then examined against variations between the healthy machines in order to determine the loads and the fault severities in which the feature can reliably detect the faults. The results show that the feature based on the EPVA (extended Park’s vector approach) is the best method. This feature can detect turn to turn faults with a severity of 3.5% or greater at loads greater than 20% and phase to phase turn faults with a severity of 1.7% or greater under all loading conditions. However, estimating the fault severity is generally found to be difficult. The thesis also examines the feasibility of detecting static eccentricity faults using the different types of sensor signals under ten different loading conditions. The thesis compares potential eccentricity features under nine different fault severities. The useful features are identified and then combined through weighted linear combination (WLC) in order to produce a better eccentricity fault indicator. The indicator begins to show significant magnitude variation when the fault severity is greater than or equal to 25% and the load is greater than or equal to 25%. The experimental results show that detecting the static eccentricity faults is possible but estimating the fault severity may be difficult. Furthermore, the effects of misalignment faults on the useful eccentricity features are investigated. In this thesis, the analysis of broken rotor bar faults is performed under motor starting and rundown operation. The starting analysis introduces a new approach to detect broken rotor bar faults that utilises the wavelet transform of the envelope of the starting current waveform. The results of the wavelet transform are then processed in order to develop a normalised parameter, called the wavelet indicator. It is found that the wavelet indicator can detect a single broken bar under all loading conditions during motor starting operation. The indicator also increases its magnitude as the severity of the fault increases. On the other hand, the rundown analysis proposes several broken rotor bar fault detection techniques which utilise the induced voltage in the stator windings and the stator magnetic flux linkage after supply disconnection. The experimental results show that detecting the faults during rundown is generally difficult. However, the wavelet approach, which is based on monitoring changes in the motor torque for a given slip, seems to give the best result. / Thesis (Ph.D.) -- University of Adelaide, School of Electrical and Electronic Engineering, 2008

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 198-201). Also available on the Internet.

Le moteur électrique est l’un des organes principaux d’un véhicule électrique. Sa température, notamment celle des bobines, doit être réduite pour éviter toute dégradation. Le refroidissement par l’extérieur, comme avec une chemise d’eau dans le carter, apparait limité car les pertes générées dans les bobines doivent traverser des zones où la conduction thermique est très mauvaise. L’extraction des calories au cœur de la machine est préférable, mais les échanges thermiques avec l’air sont modérés. En application automobile, le moteur électrique est situé à proximité d’un circuit d’huile de lubrification. Le refroidissement par l'huile en contact direct avec les bobines est étudié.La thèse s’est d’abord attachée à la recherche bibliographique étendue sur les différentes solutions de refroidissement de moteur. Ensuite, les transferts thermiques à l’intérieur du moteur ont été modélisés par méthode nodale. A travers une étude de sensibilité, les principales améliorations thermiques passives ont été dégagées, puis les systèmes de refroidissement eux-mêmes ont été modélisés. Enfin, des essais ont été réalisés sur un banc spécialement conçu. Pour cette partie expérimentale, le refroidissement direct des bobines par circulation d’huile a été étudié en détail. Différents types d’injecteurs d’huile sur les têtes de bobine ont été testés dans diverses conditions de vitesse du rotor, température et débit d’huile.L’objectif de cette thèse est d’analyser l’ensemble des problématiques thermiques liées aux solutions de refroidissement à huile. Il s’agit d’une étude comparative de la performance des solutions à huile entre elles et avec celle d’un refroidissement à eau plus conventionnel. / Electric motor is one of the most important elements of an electric vehicle. Some elements, particularly the windings, can be affected by rising heat. External cooling, as water jacket in the case, appears to be limited because the losses generated in windings must pass through zones where conduction is very poor. Cooling in the core of the machine is preferable, but heat transfer with air is poor. Due to the presence of lubricating oil in the vicinity of the motor and the heat transfer enhancement that such a liquid provides, oil circulation on the windings has been considered.The research was first dedicated to an extensive bibliography on the different solutions of motor cooling. Then heat transfer within the motor was modelled by using the lumped system analysis. Thanks to a sensitivity analysis, the main parameters affecting temperature have been identified before cooling systems were modelled. Finally, tests were performed on a specially designed bench. Oil was introduced at each side of the machine to directly cool the stator coil end-windings. Several oil injection patterns were tested. The influence of the oil flow rate, rotation speed and oil temperature has been investigated.The objective of this PHD study is to analyse all the thermal issues related to the oil cooling systems. This is a comparative study of the performance of the oil cooling solutions. Comparison is also done with conventional water cooling.

Este trabalho faz uma introdução à evolução dos processos de laminação a frio, acionamento e controle dos mesmos, com foco na laminação de encruamento. O principal objetivo é estabelecer um modelo linear dos sistemas de acionamento, que permita o projeto de um controle multivariável. Pretende-se que a robustez do controle multivariável contribua para a eliminação de defeitos associados aos processos de bobinamento e desbobinamento. A eliminação destes defeitos traz um grande retorno econômico em função do grande volume de produção destas instalações. Para isto é desenvolvido um modelo matemático do sistema completo. No modelo são evidenciadas não linearidades associadas à variação dos diâmetros e inércias das bobinas na desenroladeira e enroladeira. Para solucionar esse problema as parcelas contendo as não linearidades são removidas do modelo. Posteriormente essas parcelas são repostas através de malhas feedforward no controle. Para validar o modelo são projetados controladores PID semelhantes aos utilizados no laminador real. Com os resultados obtidos através de simulação, discute-se a validade do modelo comparando-os com os dados do processo real. A partir desse modelo é desenvolvido o modelo linear em espaço de estados, a ser utilizado no projeto do controlador robusto multivariável. Em seguida é desenvolvido o projeto deste controlador multivariável utilizando a técnica LQG/LTR. Finalmente, são discutidos os resultados das simulações, comparando-os com os dados reais da planta. De um modo geral, os resultados apontam para uma boa aproximação entre a planta real e o modelo proposto. / This work is an introduction to the evolution of the processes of cold rolling, drive and control, focusing on skinpass rolling. The main objective is to establish a model of linear drive systems, allowing the design of a multivariable control. It is intended that the robustness of multivariable control contributes to the elimination of defects associated with processes of coiling and uncoiling. The elimination of these defects poses a great economic return due to the large volume of production of these facilities. To achieve this deal it was developed a mathematical model of the complete system. Nonlinearities associated with variation in diameters and inertia reels in desenroladeira and reel are evidenced in the model. To solve this problem the terms containing nonlinearities were removed from the model and, subsequently reintroduced by feedforward control loops. To validate the model, PID controllers were designed in a similar way to those used in real mill. With the results obtained by simulation, we discuss the validity of the model by comparing them with the actual process data. From this model it was developed a linear state space model to be used in the design of robust multivariable controller. After that it was developed the design of this multivariable controller using the technique LQG / LTR. Finally, it was discussed the simulation results, comparing them with actual data of the plant. Overall, the results point to a good approximation of the real plant and the proposed model.

This thesis analyses the behavior of an induction motor based on a mathematical model created for its simulation. The model describes the interaction of its several non linear differential equations to present a simulated output of induced torque and mechanical speed. Considering the applications to marine propulsion, it is also the goal of the project to design and test a control system for the speed of the motor by maintaining a specific cruse speed regardless the perturbations. / by Camilo Carlos Roa. / Thesis (M.S.C.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

Este trabalho traça um panorama dos PLCs e tecnologias associadas em momentos anteriores e posteriores à publicação da norma IEC61131-3 e discute aspectos relativos à sua adoção. A aplicação deste norma pode trazer ganhos de produtividade no projeto e implementação de sistemas de automação industrial. Esta dissertação apresenta o caso do "Projeto de modernização dos navios-varredores da Marinha do Brasil" no qual alguns dos conceitos desta norma foram utilizados com sucesso. Ferramentas e metodologias desenvolvidas para adequar o PLC existente a alguns requisitos da norma são descritas ao longo da dissertação. A operação do novo sistema de varredura pode ser verificada através dos resultados experimentais apresentados. / This work presents an overview of the PLC and associated technologies before and after the publication of the IEC61131-3 standard. Some aspects concerning the adoption of this standard are also discussed. The application of this standard can increase productivity in the design and implementation of industrial automation systems. Some concepts of this standard were applied, succesfully, to the modernization of the Brazilian Navy mine-sweepers. Tools and methods that were required in order to adapt the existing PLC to the IEC standard are described. The operation of the newly developed system can be verified by experimental results.