As increasing power requirement in more or all electric aircraft, electric power system is required to be more efficient and lower in weight. Among the current power generation technologies, 115V variable frequency (VF) system and 270VDC system are regarded as the two optimal options for future use in MEA or AEA. Therefore, it is very important to compare their relative merits in order to determine the optimal choice on the primary power type. As the reviewed literature mainly represents the comparison between 270VDC system and 115V constant frequency system, it is very necessary to conduct the comparison between 270VDC system and 115V/VF system. The aim of this study is to grasp the nature of these systems and evaluate these two systems in terms of some engineering aspects. Literature regarding the power generation technology is first investigated. Based on initial comparison, the 270VDC brushless generating system and 115V VF generating system are selected for this study. Before conducting system architecture design and wiring system design, the load requirement analysis and optimization are conducted. Finally, a comparison between these two systems will be made in terms of weight, power off take, minimum voltampere (VA) capacity requirement, voltage drop, reliability, life cycle cost and risk. The results show that the 270VDC system is superior to the115V/VF system in terms of weight and efficiency. With regards to system reliability, the 270VDC system can be designed as either an active parallel system or a standby system while the 115V/VF system can only be designed as a standby redundant system. As far as risk is concerned, the 270VDC is more dangerous than the 115V/VF system in terms of arcing risk and corona discharge. All in all, the 270VDC system can be considered as the optimal choice for future use in AEA or MEA.

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 distortion can negatively impact the performance of other sensitive loads in the system. If a VFD serves a critical function, it may be necessary to supply the VFD from a Diesel Generator or Uninterruptible Power Supply (UPS). These sources have relatively high impedance when compared to a standard utility source, and will result in greater harmonic voltage distortion. This increases the likelihood of equipment failure due to harmonics. The full extent of the impact, however, is typically unknown until an extensive harmonic analysis is performed or the system is installed and tested. This thesis evaluates the impact that source impedance has on the harmonic voltage distortion that is produced by nonlinear loads such as VFDs. An ideal system of varying source types (Utility, Generator and UPS) and varying VFD rectifier technologies (6-Pulse, 12-Pulse and 18-Pulse) is created to perform this analysis and plot the results. The main output of this thesis is a simplified methodology for harmonic analysis that can be implemented when designing a power system with a VFD serving a critical function and a high impedance source like a generator or UPS. Performing this analysis will help to ensure that other sensitive loads will operate properly in the system. / Master of Science

When polymer power cables were introduced into mediumvoltage applications in the late 1960s, the degradationphenomenon later referred to aswater treeingwas still unknown. However, this changedwithin a relatively short space of time. Just 5-10 years afterthese first polymer applications, faults began to appear thatcould be attributed to the new phenomenon-water treeing. Sincethen, cable manufacturers have been improving their designsgradually, and cables produced today are assumed to have muchlower susceptibility to water trees. However, water treeing isstill assumed to be the most important degradation process inthese applications. There are huge amounts of polymer cable installations thatare degraded by water trees. Since many of these cables areinstalled in the same grid nets, one cable fault oftengenerates another. If two or more cables fail at the same time,the consequences can be extensive. A non-destructive diagnosticmethod makes it possible to assess cables and take action priorto failures. This thesis presents the results of research work on thedevelopment of a measurement technique and diagnostic methodfor the assessment of medium voltage XLPE cables in the field.The method used is called high voltage dielectric spectroscopy,and involves the measurement of capacitance and loss as afunction of frequency at high voltages. The method is used in ashort frequency range of approximately one decade in thelow-frequency region (normally from 1 down to 0.1 Hz). Thevoltage levels used initially are all below the service-voltagelevel. If the cable is assessed to be free from water trees, aslightly increased voltage can be used. Based on dielectric-spectroscopy measurements, specificwater-tree analysis and breakdown tests, a set of measurementprocedures and criteria that take into account differences incable designs has been proposed for the assessment of mediumvoltage XLPE cables. The characteristic responses of XLPEcables (in both non and water-tree-deteriorated cases) make itpossible to separate the cable response from the influence ofaccessories. Field experience shows thatwater-tree-deteriorated cables with relatively low breakdownstrengths can remain in service for many years. <b>Keywords:</b>dielectric spectroscopy, high voltage,variable frequency, diagnostics, non-destructive diagnostics,cables, medium voltage, polymer, XLPE, water trees, watertreeing

The objectives of the proposed research are to model, optimize, and control variable frequency microwave (VFM) curing of polymer dielectrics. With an increasing demand for new materials and improved material properties, there is a corresponding demand for new material processing techniques that lead to comparable or better material properties than conventional methods. Presently, conventional thermal processing steps can take several hours. A new thermal processing technique known as variable frequency microwave curing can perform the same processing steps in minutes without compromising the intrinsic material properties. Current limitations in VFM processing include uncertain process characterization methods, lack of reliable temperature measuring techniques, and the lack of control over the various processes occurring in the VFM chamber. Therefore, the proposed research addressed these challenges by: (1) development of accurate empirical process models using statistical experimental design and neural networks; (2) recipe synthesis using genetic algorithms; (3) implementation of an acoustic temperature sensor for VFM process monitoring; and (4) implementation of neural control strategies for VFM processing. and #8194;

This paper designs and implements a DSP-microprocessor based variable frequency motor drive. We control the induction motor with V/F scheme. This paper also analysis about Sine-PWM and Space-Vector-PWM. Compared with commonly used SPWM method, SVPWM has the advantages of higher voltage utilization, lower harmonic and lower switching loss. Also, it increases the efficiency of an inverter. To calculate duty cycle this paper support different update model, so symmetrical and asymmetrical PWM are generated. To analyse about spectra, and we can find the asymmetrical PWM restrain the harmonic.

Abstract: This paper designs and implements a DSP-microprocessor based motor driver. We control the induction motor with V/F scheme. And we module all circuits with PCB Layout.This Inverter is compose of digital board and analog-power board. We connect two parts, and we use a three phase induction motorto to be the load. Because the digital board is compose of DSP, it is to fit a lot of mathematics. It is easy to use the software to present the theory. So the paper compute the three phase gate signals with asymmetrical Pulse-Width-Modulation model.

<p>When polymer power cables were introduced into mediumvoltage applications in the late 1960s, the degradationphenomenon later referred to as<i>water treeing</i>was still unknown. However, this changedwithin a relatively short space of time. Just 5-10 years afterthese first polymer applications, faults began to appear thatcould be attributed to the new phenomenon-water treeing. Sincethen, cable manufacturers have been improving their designsgradually, and cables produced today are assumed to have muchlower susceptibility to water trees. However, water treeing isstill assumed to be the most important degradation process inthese applications.</p><p>There are huge amounts of polymer cable installations thatare degraded by water trees. Since many of these cables areinstalled in the same grid nets, one cable fault oftengenerates another. If two or more cables fail at the same time,the consequences can be extensive. A non-destructive diagnosticmethod makes it possible to assess cables and take action priorto failures.</p><p>This thesis presents the results of research work on thedevelopment of a measurement technique and diagnostic methodfor the assessment of medium voltage XLPE cables in the field.The method used is called high voltage dielectric spectroscopy,and involves the measurement of capacitance and loss as afunction of frequency at high voltages. The method is used in ashort frequency range of approximately one decade in thelow-frequency region (normally from 1 down to 0.1 Hz). Thevoltage levels used initially are all below the service-voltagelevel. If the cable is assessed to be free from water trees, aslightly increased voltage can be used.</p><p>Based on dielectric-spectroscopy measurements, specificwater-tree analysis and breakdown tests, a set of measurementprocedures and criteria that take into account differences incable designs has been proposed for the assessment of mediumvoltage XLPE cables. The characteristic responses of XLPEcables (in both non and water-tree-deteriorated cases) make itpossible to separate the cable response from the influence ofaccessories. Field experience shows thatwater-tree-deteriorated cables with relatively low breakdownstrengths can remain in service for many years.</p><p><b>Keywords:</b>dielectric spectroscopy, high voltage,variable frequency, diagnostics, non-destructive diagnostics,cables, medium voltage, polymer, XLPE, water trees, watertreeing</p>

This study examines five potential improvement projects that could be implemented at the Continental Tire manufacturing plant located in Mount Vernon, IL. The study looks at insulating of tire molds, installation of variable frequency drives on circulating pumps, pressure reduction turbines, waste heat utilization used for absorption cooling, and cogeneration using a gas turbine cycle. A feasibility study and cost analysis was performed for each project to determine recommendation for implementation. The two most appealing projects are the insulation addition and the installation of variable frequency drives. Adding insulation would produce energy savings in the range of 908 kJ/s (3,097 Btu/hr) to 989 kJ/s (3,374 Btu/hr) and annual savings between $13,390 and $14,591. Installation of variable frequency drives on two 200 hp circulating pumps would produce energy savings between 74.6 kW (100 hp) and (104.6 kW (140.2 hp) with annual monetary savings in the range of $41,646 to $58,384.

This study examined the Lake of Egypt Power Plant operated by Southern Illinois Power Cooperative located on the Lake of Egypt south of Marion, IL. The facility has a 173 MW rated turbine operating on a pulverized coal cyclone boiler and three 33 MW rated turbines operating on an oversized circulating fluidized bed boiler with 120 MW capacity. The first area examined was reduction of auxiliary power consumption possible with the addition of variable frequency drives to the forced draft fan and booster fan motors. Included in this examination was an analysis of the economic and environmental impact of such a reduction. From the analysis an annual savings of 24.4 GWh of electricity is possible. The second area examined was the generation capacity lost due to condenser fouling and the possible reduction in facility emissions with altered condenser treatment. From the analysis an additional 3.0 MW of capacity facility wide is possible or a reduction steam production of 1.5% for each boiler.

<p> The speed of a squirrel-cage induction motor is controlled by varying the supply frequency. The design of an SCH controlled inverter, using gating from a logic unit to give a variable-frequency power-level output, is described.</p> / Thesis / Master of Engineering (MEngr)