Historical attempts to measure forces in magnetic bearings have been unsuccessful as a result of relatively high uncertainties. Recent advances in the strain-gauge technology have provided a new method for measuring magnetic bearing forces. Fiber optic strain gauges are roughly 100 times more sensitive than conventional strain gauges and are not affected by electro-magnetic interference. At the Texas A&M Turbomachinery Laboratory, installing the fiber-optic strain gauges in magnetic bearings has produced force measurements with low uncertainties. Dynamic flexibility transfer functions exhibiting noticeable gyroscopic coupling have been identified and compared with results of a finite element model. The comparison has verified the effectiveness of using magnetic bearings as calibrated exciters in rotordynamic testing. Many applications including opportunities for testing unexplained rotordynamic phenomena are now feasible.

This thesis has been performed in order to earn a master's degree in electrical engineering. The task was to implement an automatic voltage regulator, AVR, to control the terminal voltage of the synchronous generator Svante at the Division of Electricity at Uppsala University. The AVR uses Bluetooth technology to transfer a control signal produced by a programmable logical controller, PLC, to phase- mounted SSRs that decides what proportion of the AC from a six-phase brushless exciter that is to be used for the magnetization of the rotor. Test runs of the AVR were preformed with a regulator optimized according to the Ziegler-Nichols method and a static exciter that uses brushes and slip rings to apply voltage to the rotor winding. The results obtained complies with the assigned requirements set for this thesis and the AVR. The primary focus of this thesis mainly lies in the construction of the control system, which include the programming of both PLC and Bluetooth communicating devices.

Historical attempts to measure forces in magnetic bearings have been unsuccessful as a result of relatively high uncertainties. Recent advances in the strain-gauge technology have provided a new method for measuring magnetic bearing forces. Fiber optic strain gauges are roughly 100 times more sensitive than conventional strain gauges and are not affected by electro-magnetic interference. At the Texas A&M Turbomachinery Laboratory, installing the fiber-optic strain gauges in magnetic bearings has produced force measurements with low uncertainties. Dynamic flexibility transfer functions exhibiting noticeable gyroscopic coupling have been identified and compared with results of a finite element model. The comparison has verified the effectiveness of using magnetic bearings as calibrated exciters in rotordynamic testing. Many applications including opportunities for testing unexplained rotordynamic phenomena are now feasible.

As an alternative to converting a brushless exciter to static excitation in order to improve an exciter’s response time, conversion of the existing conventional brushless exciter is possible. A high initial response (HIR) brushless excitation system has the ability to force its output to ceiling voltage in 0.1 second or less, which is a response time similar to a static excitation system. To achieve the required fast response time, various modifications to the existing exciter components are required, including the ac exciter stator, permanent magnet generator (PMG), and voltage regulator. This paper describes those required modifications and associated technical information. This paper presents a concept solution that decreases the response time of a brushless exciter in order to respond to grid disturbances via the excitation system, while minimizing modification of the existing excitation system configuration.

O presente trabalho visa estabelecer uma metodologia alternativa para o levantamento dos principais transitórios elétricos sofridos por excitatrizes brushless, decorrentes de transitórios ocorridos na armadura do gerador principal. O método consiste no cálculo, a partir de dados de projeto, dos parâmetros que compõem os circuitos equivalentes do gerador principal e da excitatriz, seguido de simulações, em ambiente PSIM®, dos piores casos de transitórios de tensão e corrente sofridos pela armadura do gerador principal, como curtos-circuitos monofásicos, bifásicos e trifásicos, operação assíncrona do gerador principal e sincronização com defasagem entre as tensões do gerador e da rede. Em cada caso, monitoram-se as tensões e correntes resultantes nos diodos da ponte retificadora rotativa. Resultados simulados e experimentais são comparados. / This study aims to establish an alternative methodology for determining the main transients on brushless exciters due to transients in the main generator armature. The method consists in calculating, from design data, the parameters of the equivalent circuits of the main generator and the exciter, followed by simulations, with the software PSIM®, of the worst voltage and current transient cases in the main generator armature, like single-phase, dual-phase and three-phase short circuits, asynchronous running of the main generator and out of phase synchronization. In each case the currents and voltages of the rotative bridge diodes were monitored. Simulation and experimental results are compared.

This thesis aims to simulate and find out more about the electrical dynamics of a six-phase exciter for hydropower generators. Because ordinary electric circuit-based simulation software only simulate three-phase electrical systems, a FEM-based software is used for the electrical dynamics simulations of the six-phase system. The objective is to analyse the pulsation behaviour of the rectified electrical output on the six-phase system and compare it to the three-phase system. The three-phase system is also simulated with filters with the aim of decreasing the amplitude of the pulsations on the electrical output. It is expected that an upgraded system from a three-phase system to a six-phase system should double the pulsation frequency on the rectified electrical output. However, the result shows that the rectified electrical output of the six-phase system consists of pulsations with unexpected frequencies. The simulated RL-filter on the three-phase system shows only insignificantly small changes on the rectified electrical pulsation amplitude.

This thesis aims to simulate and find out more about the electrical dynamics of asix-phase exciter for hydropower generators. Because ordinary electric circuit-basedsimulation software only simulate three-phase electrical systems, a FEM-basedsoftware is used for the electrical dynamics simulations of the six-phase system. Theobjective is to analyse the pulsation behaviour of the rectified electrical output on thesix-phase system and compare it to the three-phase system. The three-phase systemis also simulated with filters with the aim of decreasing the amplitude of the pulsationson the electrical output.It is expected that an upgraded system from a three-phase system to a six-phasesystem should double the pulsation frequency on the rectified electrical output.However, the result shows that the rectified electrical output of the six-phase systemconsists of pulsations with unexpected frequencies. The simulated RL-filter on thethree-phase system shows only insignificantly small changes on the rectified electricalpulsation amplitude.

O presente trabalho visa estabelecer uma metodologia alternativa para o levantamento dos principais transitórios elétricos sofridos por excitatrizes brushless, decorrentes de transitórios ocorridos na armadura do gerador principal. O método consiste no cálculo, a partir de dados de projeto, dos parâmetros que compõem os circuitos equivalentes do gerador principal e da excitatriz, seguido de simulações, em ambiente PSIM®, dos piores casos de transitórios de tensão e corrente sofridos pela armadura do gerador principal, como curtos-circuitos monofásicos, bifásicos e trifásicos, operação assíncrona do gerador principal e sincronização com defasagem entre as tensões do gerador e da rede. Em cada caso, monitoram-se as tensões e correntes resultantes nos diodos da ponte retificadora rotativa. Resultados simulados e experimentais são comparados. / This study aims to establish an alternative methodology for determining the main transients on brushless exciters due to transients in the main generator armature. The method consists in calculating, from design data, the parameters of the equivalent circuits of the main generator and the exciter, followed by simulations, with the software PSIM®, of the worst voltage and current transient cases in the main generator armature, like single-phase, dual-phase and three-phase short circuits, asynchronous running of the main generator and out of phase synchronization. In each case the currents and voltages of the rotative bridge diodes were monitored. Simulation and experimental results are compared.

The purpose of this thesis is to validate generator models for dynamic studies of power systems using PSS/E (Power System Simulator for Engineering), EMTP (ElectroMagnetic Transient Program), and Hypersim. To thoroughly evaluate the behavior of a power system in the three specified software packages, it is necessary to have an accurate model for the power system, especially the generator which is of interest. The effect of generator modeling on system response under normal conditions and under faulted conditions is investigated in this work. A methodology based on sensitivity analysis of generator model parameters is proposed aiming to homogenize the behavior of the same power system that is modeled in three software packages. Standard IEEE 14-Bus system is used as a test case for this investigation. Necessary changes in the exciter parameters are made using the proposed methodology so that the system behaves identical across all three software platforms.

Os novos materiais utilizados nas estruturas de aeronaves, mais leves e flexíveis, tornam estas estruturas mais sujeitas a fenômenos aeroelásticos, sendo que o mais sério deles é o flutter, que deve ser cuidadosamente investigado com uma boa campanha de ensaios em vôo durante o desenvolvimento e certificação da aeronave. Este trabalho propõe um projeto conceitual de um excitador de flutter que atenda às necessidades dos ensaios, tentando resolver problemas encontrados nos modelos utilizados comumente. Para isso, é feita uma revisão da literatura pertinente, apresentando conceitos de ensaios em vôo e do fenômeno em questão, além de apresentar um histórico dos ensaios e modelos de excitadores utilizados ao longo da história. Em seguida, são apresentados alguns conceitos de excitadores, que são dimensionados e analisados segundo suas vantagens e desvantagens para finalmente escolher o modelo mais pertinente visando no futuro um projeto detalhado, construção e testes em túnel de vento. / The ultimate materials used in aircraft structures, lighter and more flexibles, make these structures more susceptible to aeroelastic phenomena including flutter, the most dangerous of all. This kind of phenomena must be carefully investigated with satisfactory flight test campaigns during the aircraft development and certification. This work proposes a flutter exciter conceptual design that attends the test necessities, trying to solve problems found in the models used actually. So, a bibliographic revision is done, presenting flight test concepts and the studied phenomena, regarding a flight test history and the exciter models used through the years. Finally, some exciter concepts are presented, dimensioned and analyzed considering their advantages and disadvantages in order to choose the most pertinent model, considering, in a near future, the detailed design, manufacturing and wind tunnel tests.