Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 108 for “"unbalance"”.
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Voltage Unbalance-Cognizant Optimization of Distribution Grids
… the distribution grid has exacerbated voltage unbalance issues leading to greater risks of reducing equipment lifetime, equipment damages, and increased ohmic losses. Most approaches to regulating voltage in distribution systems only focus on voltage magnitude and neglect phasor discrepancies …
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Influence of Induced Unbalance on Subsynchronous Vibrations of an Automotive Turbocharger
… levels. It is theorized that an increase in unbalance could cause a reduction in subsynchronous vibration amplitudes. Through the use of a custom turbocharger, a series of unbalances were applied to both the turbine and compressor wheels and the resulting amplitudes were recorded off a …
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The impact of voltage unbalance and regulation on the life expectancy of LV induction machines
… utilities can lead to them being operated under unbalanced voltage conditions. Power utilities experience voltage unbalances and voltage dips when they provide services to end users. In South Africa ESKOM is the primary power utility, it has a license agreement with NERSA stipulating the …
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Reclosing transients in standard and premium efficiency induction machines in the presence of voltage unbalance
… and torque transients in the presence of voltage unbalance. Voltage unbalance presents a power quality issue which can potentially have a negative effect on the efficiency of an induction machine. Both machines were tested for 0%, 1% and 2% voltage unbalance with a focus on start-up and 180° …
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Critical speeds and unbalance response of cantilever-sleeve rotors using finite elements with efficient higher order basis functions
… the determination of their critical speeds and unbalance response. Dynamic behavior of simple rotor systems can be studied using analytical techniques. However, for complex rotor systems it is necessary to use approximate techniques. The finite element method is one such approximate technique …
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Design and implementation of a 500 kVAr hybrid power factor
… and test a 500 kVA-hybrid power factor/current unbalance correction unit. The unit will be used to reduce the maximum demand and reactive power consumption through power factor correction of large electricity users as well as minimize power disruption and improve power quality through unbalance …
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Impact of plug in electric vehicle battery charging on a distribution system
… the distribution system in terms of voltage unbalance and transformer overloading. Although PEV battery charging is increasing, impact on the distribution system is not fully understood. This study focuses on voltage unbalance caused by uneven distribution of PEV penetration among the phases. …
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Oil-whirl instability in an automotive turbocharger
… UK, based on test data using two different unbalance levels on a turbocharger. The test with the high unbalance indicated that there was shift in the sub-synchronous frequency to synchronous frequency between about 80,000 rpm to 130,000 rpm. The literature suggests that this self-excited …
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The Formulation of a Novel Control Framework for Regulation of an Active Low Voltage Network
… issues arising from excess supply or load unbalance. As LV networks and power systems were not designed with these entities in mind, scalable and flexible mitigation strategies will be needed to tackle these problems. This general conclusion was determined in the literature. This …
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Operation of induction machines in the presence of unbalanced supplies
… voltages. However, the power system experiences unbalanced voltages, overvoltages, undervoltages, etc, which are seen at the motor terminals. The South African Electricity Supply Utility (Eskom) supplies the commercial and industrial systems with a line voltage range of 400V +- 10%. An Induction …
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Induction motor variable speed drive performance and impact on energy savings
… voltage of 340 to 440. In urban areas 2% voltage unbalance is considered acceptable, while 3% voltage unbalance is considered acceptable for rural areas. The combined effects of under or overvoltages coupled with "acceptable maximum" voltage unbalance is not understood or documented. This project …
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Impact of plug in electric vehicle battery charging on a distribution system based on real-time digital simulator
… in terms of maximum voltage deviation, voltage unbalance at various locations, transformers overloading, and introducing new peaks into the system. In this research, a 12.47 kV real distribution network has been modeled using real time digital simulator, using real data from a power distributor. …
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Analysis, Simulation, and Measurement of Micro-Vibrations in Reaction Wheels for High-Performance Imaging Missions
… These vibrations, resulting from mechanical unbalance, torque ripple, and bearing imperfections, propagate through the satellite structure and induce line-of-sight (LoS) jitter. This thesis presents the analysis, simulation, and measurement of reaction wheel micro-vibrations to characterise …
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Voltage Balancing Techniques for Flying Capacitors Used in Soft-Switching Multilevel Active Power Filters
… static high power converters. However, voltage unbalance of the clamping capacitors in the active filter in practical applications was observed due to its unequal parameters. Thus, the fundamentals of flying capacitors were characterized dealing with voltage balancing between flying capacitors …
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AUTOMATIC ON-LINE FAULT DETECTIONALGORITHM FOR HYDRAULIC TURBINES
… the origin of the vibration, for example unbalance, misalignment and so on. In this thesis, first of all I describe the main methods that I have used for writing the fault detection algorithm and then I apply the fault detection algorithm on RTR simulation model in MATLAB environment to …
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Probabilistic assessment of the impact of plug-in electric vehicles on power quality in electric vehicles on power quality in electric distribution systems.
… voltage imbalance, transformer overload and unbalance are investigated in this thesis. Since the problem is of a stochastic nature, a probabilistic approach using Monte Carlo simulation is adopted in this work to assess potential impact on power quality in the distribution system and hence …
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Test and analysis methods for resolving fan/motor vibration problems in air-conditioning units
… units that are excited by fan impeller unbalance, taking into account the gyroscopic effect of the rotating fan impeller; Two air-conditioning units were investigated in the project. They were designated as test units #1 and #2. For the test unit #1 and test unit #2, the vibration …
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Design and development of intelligent computational techniques for power quality data monitoring and management
… non-linear loads faces the problem of voltage unbalance, sag, swell, momentary or temporary interruption and ultimately complete outage of EPDS. The PQ problems have motivated power system engineers to design and develop new methodologies and techniques to enhance EPDS performance. To do so, …
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Studies on the Motion of Continuous Viscoelastic Rotors
… The coupling is effected through the shaft unbalance forcing terms. In this study, both coupled and uncoupled motion is considered.
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