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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 79 for “"variable-frequency"”.
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Variable Frequency Microwave Curing of Polyurethane
… PUR, and (2) if there was an effect of microwave frequency on the cure rate. The primary tool for determining extent of cure in the PUR samples was Fourier transform infrared spectroscopy (FTIR). Using this characterization method, the changes in intensities of four bonds specific to the PUR …
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Crystallization of Lithium Disilicate Glass Using Variable Frequency Microwave Processing
… over conventional processing techniques. Variable frequency microwave (VFM) processing is an advanced processing technique developed to overcome the hot spot and the arcing problems in microwave processing. In general, two main questions are addressed in this dissertation: 1. How does …
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Voltage Stability and Control in Autonomous Electric Power Systems with Variable Frequency
… this extent a controller based on the model of a variable frequency synchronous generator has been developed and tested. The results obtained show a considerable improvement performance when compared to previous practices.
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Impact of System Impedance on Harmonics Produced by Variable Frequency Drives (VFDs)
Variable Frequency Drives (VFDs) are utilized in commercial and industrial facilities to improve motor efficiency and provide process flexibility. VFDs are nonlinear loads that inject harmonic currents into the power system, and result in harmonic voltages across the system impedance. This harmonic …
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High-Fidelity Power Injection From A Fuel Cell Onto A Variable-Frequency AC Power Bus
… trade-offs are especially significant in highly variable-frequency systems where the phase-detector response time may be critical. Variable-frequency power systems exist in isolated power systems with low inertia such as microgrids and ships, and on aircraft due to the main generators being …
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Real-Time Path Integral Simulations of Variable Frequency Phonons and Spin Reservoirs in Condensed Materials
… integral formulations is made in the context of variable frequency oscillators. Particular attention is paid to the motion of impurities in a semiconductor lattice and reverse isotopic effects arising due to variable frequency oscillator coordinate(s). In addition, a comparison is made between …
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A Method for Evaluating the Application of Variable Frequency Drives with Coal Mine Ventilation Fans
… band of air pressures and quantities. The use of variable frequency drives (VFDs), which control fan speed, provides a solution to this problem. VFDs are already used in various similar applications such as pumping and building ventilation. New technology now enables efficient VFD operation in …
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Single frequency whole-body impedance studies in children with diarrhoeal disease and development of a variable frequency system
… This WBI technology, which operates at a single frequency, has been applied to the assessment of dehydration in children with diarrhoeal disease. The normal range of WBI was determined on a group of normally hydrated children and was found to have a mean of 746 Ω, a standard deviation of 85 Ω and …
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An Open Loop Feed-Forward Control Scheme for Bioinspired Artificial Hair Cell Sensors
… differences in system response during constant frequency and variable frequency excitation. In constant frequency testing, artificial hair cell sensors were excited at 100 Hz across a range of input intensities to observer current output response during increasing or decreasing excitation …
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Development of terahertz diffractive optics and plasmon-phonon polaritonics components /
… development of terahertz diffractive optics and variable frequency polaritonic infrared optical components is described. Development and performance of direct laser ablation fabricated multilevel phase Fresnel lenses and metal Soret zone plates for focusing of 0.6 and 4.7 THz frequency radiation …
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Single Degree of Freedom Solid Rotor Velocity Control Induction Drive
… (PI) controller applying a constant amplitude, variable frequency drive. The stator consists of six iron teeth, evenly spaced and pointing radially inward, wound with 160 turns of copper wire each in a three-phase, two-pole configuration. A steel enclosure houses the stator and is supported by a …
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Light Emission from Zinc Oxide Nanoforest Plasma
… doped silicon. Both DC stress and AC stress with variable frequency were applied (up to 10 KHz) as well as short duration pulses (from 1 to 100 μs) to the pads of the silicon microstructures causing excitation of free electrons in the plasma and more atomic transitions to be present compared to …
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Improvements in integrated high-quality rectifier-regulators
… spike on the switch at turn-off. In this thesis, variable frequency control, swinging choke, and low loss LC snubber techniques are proposed to alleviate these problems. Finally, several experimental converters with different specifications are evaluated with respect to efficiency and ability to …
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Zero-voltage switched resonant and PWM converters: design-oriented analysis and performance evaluation
… considers resonant converters with conventional variable frequency control and with phase-shift control, and the zerovoltage- switched full-bridge PWM converter (ZVS-FB-PWM). Also, a systematic procedure to determine all possible resonant converters with two or three reactive elements is …
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Design of a 1-200 MHz signal generator
… develop a wideband RF signal generator with a frequency range of 1 - 200MHz to the following specifications: • output at 50Q • stable output • signal amplitude control • continuously variable frequency range up to VHF band • AM modulation capability In this project, the whole range of frequency …
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A single three phase variable speed drive with unity power factor
… new proposed topology for a single three-phase variable speed drive was developed after considering the advantages and disadvantages of previous topologies. The new topology employs only six switches that form and active front-end rectifier and a four-switch inverter. The active front-end …
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Design and Comparison of Induction Motor and Synchronous Reluctance Motor for Variable Speed Applications: Design Aided by Differential Evolution and Finite Element Analysis
… in order to design a 55Kw Induction Motor for variable speed applications, posteriorly, the performance of the final design was optimized by means of Finite Element Method (FEM) and evaluated through Indirect Field Oriented Current Control (IFOCC) strategy. Likewise, an equivalent Synchronous …
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Modeling of industrial power distribution circuits for voltage sag and fault analysis
… It then investigates and develops a 24-pulse variable frequency drive (VFD) model in EMTP. The functionality of the VFD model is evaluated by using a test feeder, with a focus on its control mechanisms. The VFD is controlled with the field-oriented control (FOC) method and tuning procedures …
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ΜΕΛΕΤΗ ΣΧΗΜΑΤΩΝ ΔΙΑΜΟΡΦΩΣΗΣ ΘΕΣΗΣ ΠΑΛΜΩΝ (ΡΡΜ) ΓΙΑ ΤΟΝ ΕΛΕΓΧΟ ΑΣΥΓΧΡΟΝΩΝ ΤΡΙΦΑΣΙΚΩΝ ΚΙΝΗΤΗΡΩΝ
… IS PRESENTED AND ANALYSED WITH APPLICATIONS TO VARIABLE FREQUENCY INVERTER DRIVES. THE MOST INTERESTING AMONG THEM ARE THE DF-PPM, THE CS-E-PPM AND THE TC-PPM SIGNALS. IT HAS BEEN DEMONSTRATED THAT THE SPECTRA OF THESE SIGNALS POSSES A NUMBER OF SIGNIFICANT FEATURES SUCH AS: A) THE FUNDAMENTAL …
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