Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 93-97). Also available via the Internet.

No description available.

Synchronous turbo alternators form the basic building block of a generation scheme. Turbo alternators are highly susceptible to foreign material ingress. In industry this phenomenon is on the rise. We evaluated the effects of foreign materials on the generator and condition monitoring equipment. The sources of foreign materials and methods to reduce ingress were investigated. We further evaluated industry best-practices on foreign material exclusion. Information is scarce, as no classic research material is available on foreign material exclusion. We therefore used industry foreign material exclusion best-practices and expert opinions were gathered. Eleven global incidents of foreign material exclusion failure were investigated. The areas of interest were: types of foreign material, area of ingress, condition monitoring response, component damage, root cause and prevention. We point out that turbo alternators are vulnerable to foreign material ingress mainly due to weak foreign material exclusion practices. We categorised the foreign materials and their effects on the operational parts of the turbo generator. We found that the air gap was the most susceptible to ingress. We identified the Generator Core Monitor as a possible solution to minimising foreign material damage. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.

Thesis (M.S.)--Ohio University, March, 1982. / Title from PDF t.p.

The subject of this thesis is about the balancing of large flexible rotors which exhibit mixed modal characteristics. The objective of the research was to develop a balancing procedure to determine correction masses without trial runs. This required the determination of(a) the modal vibration vectors for each resonance, (b) the modal damping ratios,(c) the mode shapes and(d) the equivalent mass of the rotor for each mode. It was made clear from the beginning that trial runs are unavoidable either, when the mode shapes cannot be determined using an analytical or numerical method, or when there is dual vibration at normal operating speed, produced by the influence of higher unbalanced modes, is too high to allow continuous operation of the machine. Therefore, the scope of the project was limited to the possible determination of correction masses without trial runs for the vibration modes included within the normal operating range. Some studies about the minimisation or complete elimination of trial runs have been published by several authors, but a literature search revealed no reports of systematic application of these procedures to field balancing of large turbo generators. This suggested that some practical difficulties had still to be overcome, opening the possibility for further research on this area. Analysis of the rotor response demonstrated the necessity of considering the angular position of the transducers when registering the rotor vibration. It was shown that measuring in a direction other than those of the principal axes of stiffness introduces errors when determining the magnitude and phase of the correction masses. That is to say, failing to consider the effects of the transducer angular position eliminates the possibility of balancing the rotor without trial runs. This is the first time that this problem has been recognised. The procedure developed was verified using an experimental rotor rig. The successful application of the procedure to the balancing of this rotor demonstrates that balancing withouttrialrunsisnotonlyatheoreticalbutalsoapracticalpossibility. The dynamic characteristics of the rotor rig, however, were some what limited and did not cover all the possibilities considered during the project. Therefore, a more complete numerical example was also successfully solved using the computer model of a rotor with characteristics similar to those of a real turbine, and whose unbalanced distribution was not initially known by this author.

The results, based on steam demand during the 1961-1962 to 1980-1981 heating seasons, indicate the following returns on each investment for the various turbo-generators operating with steam inlet conditions of 600 psig, 825°F, extraction at 100 psig, and exhaust at 10 psis: 13.5 per cent for the 2500 KW unit, 15.1 per cent for the 3000 KW unit, 14.6 per cent for the 4000 KW unit, and 12.9 per cent for the 5000 KW unit. Total investments for the turbo-generators were as follows: $496,860 for the 2500 kw unit, $534,830 for the 3000 KW unit, $615,770 for the 4000 KW unit, and $693,190 for the 5000 KW unit. / Master of Science

In the operation of combined heating and power plants, there are two serious threats to economy as measured by fuel consumption for the service rendered. These are loss or exhaust steam to the atmosphere and, less serious, exhaust or steam to a condenser. The greater part of the heat supplied to the steam in the form of latent heat by the boilers is lost in either case. Use of exhaust steam for heating makes available a maximum amount of heat to useful purpose and consequently shows decided economical advantages over systems wherein the heating and power supplies are separate. Still further economies are possible by operating units having the best possible economy characteristics at the particular load range in question at any time. As often happens when the electrical and exhaust steam requirements vary considerably, two dissimilar types of units must be installed to maintain satisfactory economy over the complete range of load demand on the plant. When the capacities of two such units are equal or overlap in some portion or the demand range, it is evident that there should be some load condition at which either or the units could be operated with equal economy; below which condition, one unit would show the better economy, and above which, the other unit would be more suitable. The Virginia Polytechnic Institute Heating and Power Plant has one back-pressure turbine and one condensing, bleeder-type turbines. Either of these units is capable of carrying the present electrical load. When, due to electrical load limitations, the low-pressure steam available is insufficient, the reducing valves installed enable either of the units to satisfactorily supply this low-pressure steam demand. However, at high electrical and low low-pressure demands, the back-pressure unit will discharge part of its exhaust steam to the atmosphere, while the condensing unit will discharge the excess supply, over and above the low-pressure demand, into the condenser. In the condenser, the circulating water removes the latent heat of the steam. The problem, then, is one of obtaining a quantitative comparison of the two machines throughout the range of seasonal variation of both electrical and low-pressure loads. The authors believe that the investigation will lead to fairly accurate results which, if used as a guide in operation, will aid considerably in preventing possible future fuel waste from the operation of the wrong unit for any particular set of conditions. / M.S.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

This thesis covers the analysis, dynamic modelling and control of an isolated selfexcited induction generator (SEIG) driven by a variable speed wind turbine. The voltage build up process of an isolated induction generator excited by AC capacitors starts from charge in the capacitors or from a remnant magnetic field in the core. A similar voltage build up is obtained when the isolated induction generator is excited using an inverter/rectifier system with a single DC capacitor on the DC link of the converter. In this type of excitation the voltage build up starts from a small DC voltage in the DC link and is implemented using vector control. The dynamic voltage, current, power and frequency developed by the induction generator have been analysed, simulated and verified experimentally for the loaded and unloaded conditions while the speed was varied or kept constant. Results which are inaccessible in the experimental setup have been predicted using the simulation algorithm. To model the self excited induction generator accurate values of the parameters of the induction machine are required. A detailed analysis for the parameter determination of induction machines using a fast data acquisition technique and a DSP system has been investigated. A novel analysis and model of a self-excited induction generator that takes iron loss into account is presented in a simplified and understandable way. The use of the variation in magnetising inductance with voltage leads to an accurate prediction of whether or not self-excitation will occur in a SEIG for various capacitance values and speeds in both the loaded and unloaded cases. The characteristics of magnetising inductance, Lm, with respect to the rms induced stator voltage or magnetising current determines the regions of stable operation as well as the minimum generated voltage without loss of self-excitation. In the SEIG, the frequency of the generated voltage depends on the speed of the prime mover as well as the condition of the load. With the speed of the prime mover of an isolated SEIG constant, an increased load causes the magnitude of the generated voltage and frequency to decrease. This is due to a drop in the speed of the rotating magnetic field. When the speed of the prime mover drops with load then the decrease in voltage and frequency will be greater than for the case where the speed is held constant. Dynamic simulation studies shows that increasing the capacitance value can compensate for the voltage drop due to loading, but the drop in frequency can be compensated only by increasing the speed of the rotor. In vector control of the SEIG, the reference flux linkage varies according to the variation in rotor speed. The problems associated with the estimation of stator flux linkage using integration are investigated and an improved estimation of flux linkage is developed that compensates for the integration error. Analysis of the three-axes to two-axes transformation and its application in the measurement of rms current, rms voltage, active power and power factor from data obtained in only one set of measurements taken at a single instant of time is discussed. It is also shown that from measurements taken at two consecutive instants in time the frequency of the three-phase AC power supply can be evaluated. The three-axes to twoaxes transformation tool simplifies the calculation of the electrical quantities.

Thesis (Ph. D.)--University of New South Wales, 2003. / Also available online.