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Energy Conversion, IEEE Transactions on

Issue 1 • Date March 1986

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Displaying Results 1 - 25 of 28
  • [Front cover]

    Page(s): c1
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    Freely Available from IEEE
  • IEEE Power Engineering Society

    Page(s): nil1
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    Freely Available from IEEE
  • [Breaker page]

    Page(s): nil1
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    Freely Available from IEEE
  • The Power Engineering Society

    Page(s): 1
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    Freely Available from IEEE
  • Field Tests and Simulation of a High Initial Response Brushless Excitation System

    Page(s): 2 - 10
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    The extremely long transmission distances associated with the Colstrip mine-mouth power plant called for stability improvement measures in the planning stages which included the application of high initial response excitation systems. The brushless excitation systems on the 819 MVA Colstrip Units 3 and 4 are designed to provide high initial response characteristics. Field tests were conducted during unit operation in which the fast large and small-signal response was successfully demonstrated. Response times are similar to that of static systems, without the use of brushes or collectors. Excitation system model constants were calculated based on hardware characteristics. Simulation results show the ability of the model to accurately reproduce the actual excitation system response. View full abstract»

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  • The Short-Run Value of Nonutility-Generated Electricity

    Page(s): 11 - 16
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    The Public Utilities Regulatory Policies Act (PURPA) of 1978 and the associated rulings of the Federal Energy Regulatory Commission (FERC) obligate the electric utilities to purchase electricity generated by qualifying facilities at the utility's avoided cost of alternative energy. They include no further indication of how this cost should be calculated and leave the actual implementation to the state's regulatory authorities. In this work, a computer simulation model was developed to study the short-run value of electricity that is generated by private entities and offered for sale to the electric utilities. Using the production simulation theory, the model determines how a set of generation units at different locations can be dispatched in the most economic way to meet a certain electric demand. The model then calculates the short-run value of nonutility-generated electricity by assuming the variable operational costs of electricity production will remain unchanged for any penetration of nonutility power. Several penetration scenarios were simulated using a hypothetical utility case. The short-run value of nonutility-generated electricity was found to increase with increased penetrations up to a maximum level before it starts decreasing as a result of the displacement of intermediate and base load capacity. Moreover, neither of the utility's marginal fuel costs calculated before and after the inclusion of the nonutility resources in the utility generation mix proved to capture the short-run value of the nonutility-generated electricity. View full abstract»

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  • Starting and Steady-State Characteristics of DC Motors Powered by Solar Cell Generators

    Page(s): 17 - 25
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    The performance of dc motors (series, separately-excited, and shunt motors) powered by a solar cell generator and loaded by two different types of loads, one a constant load and one a ventilator load, were analyzed with respect to the transient (starting) and steady state operation. Direct current motors are employed in photovoltaic water pumping systems; therefore, the understanding of the system operation and the matching of the system components (solar cells, dc motor type, and load type) are important factors of the system design. Since the solar cell generator in a nonlinear and time-dependent power supply with an output that varies with the insolation (hourly and daily), the performance characteristics of the dc motor are different when supplied by a solar cell generator than when supplied by a conventional constant voltage source. The transient solution was obtained by using an available computer program - SUPER SCEPTRE. The separately - excited (or permanent magnet) motor with a ventilator load was found to be the most suitable for the solar cell generator. The series motor is quite acceptable, but the shunt motor gives poor performance. In all cases the ventilator load is more compatible with the solar cell generator than with the constant load. View full abstract»

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  • Analysis of the Steady State Performance of the Double Output Induction Generator

    Page(s): 26 - 32
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    The steady-state performance of the variable speed constant frequency double output induction generator (VSCF-DOIG) is investigated. The generator is subjected to a strict control strategy in which the stator current is kept constant and equal to its rated value. This allows the generator to deliver rated power from its stator terminals, while from its rotor terminals a variable power output is obtained that is proportional to its rotor speed. Thus more than rated power can be extracted from the induction machine without overheating. The theoretical results of this investigation are verified experimentally. View full abstract»

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  • Stator Frame Deformation Problem in Large Diameter Hydro-Generators

    Page(s): 33 - 38
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    The hydrogenerators which have been delivered to Peace Canyon Power Station of B.C. Hydro and Power Authority are large diameter machines. In large diameter hydrogenerators the relative displacement between the rotor and stator tends to increase, and in the worst case the rotor may touch the stator. The above hydrogenerators have experienced some problems due to the deformation of the stator frame. The outline of problems and investigations performed to determine the relationship between stator deformation and split phase current is presented. View full abstract»

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  • Assessment of the Reliability of Motors in Utility Applications - Updated

    Page(s): 39 - 46
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    An Industry Assessment Study (IAS) was conducted to evaluate the present reliability of powerhouse motors and to identify design and operational characteristics which, through advanced development, offer the potential of increased motor, and therefore, power plant reliability. The primary objective of the IAS was to collect, analyze, and interpret candid, detailed information concerning motor application, operating factors, installation, manufacturer, failures and causes of failures. The survey data covers 6312 motors from 168 generating units representing 65 utilities. This data covers 40 percent of the population surveyed. The large quantity of data allows a meaningful analysis when it is broken down into smaller groupings. View full abstract»

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  • Power Conditioning Subsystems for Photovoltaic Central-Station Power Plants: State-of-the-Art and Advanced Technology

    Page(s): 47 - 53
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    Through the combined efforts of governmental agencies and laboratories, private organizations, universities and electric utilities, substantial progress has been made in bringing photovoltaic (PV) systems closer to commercial feasibility. The future availability of central station power conditioner subsystems (CS-PCS) that are efficient, safe, reliable, and economical will play a key role in the acceptance of large-scale PV energy by electric utilities. To accelerate the development of such CS-PCS hardware, the Department of Energy's Photovoltaic Division, as part of its Five Year Plan, has established a goal of a reliable, 98 percent-efficient CS-PCS that in volume production will cost $0.07/Wp. This will help make PV power economically competitive with electric power derived from conventional energy sources. Various governmental agencies and private organizations are cooperating to try to achieve this proposed goal. The combination of a dwindling federal budget for PV research and development (R&D), and the reluctance of American industry to accept the high economic risks involved in its own PV R&D efforts, could shift the leading edge of PV-PCS technology development to foreign competition, in general, and to Japanese industry, in particular. View full abstract»

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  • Life Distribution Models in Engineering Reliability (Nonrepairable Devices)

    Page(s): 54 - 60
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    This paper consists of probabilistic models of life distributions for different types of devices, with examples collected from various fields of engineering. The appropriate choice of the model should be based on the conception of the failure rate function and on the related failure data for a given class of devices. Using this approach may assist engineers in choosing an adequate probabilistic model. View full abstract»

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  • Asymptotics of Moments of Order Statistics and Failure Occurrence Sequences

    Page(s): 61 - 67
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    The purpose of this paper is to develop new analytical techniques for the computation of asymptotics of the Laplace transforms (moments) of order statistics for several underlying distributions, among them the truncated Weibull and Makeham-Gompertz distributions. One of the main reasons to use moments of order statistics is their importance in practical applications for solving economic and technical problems in near real time. For example, with such techniques, one can form simple expressions for expectations of early failure times of big (multi-component) systems compounded from similar components. Applied statistics, optimal life-testing, operations research and prediction theory are also possible fields of applications of the approach developed here. The method presented here permits one to calculate estimates of remainder terms giving, thereby, the possibility of improving the precision of a result by increasing the number of terms in an expansion. View full abstract»

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  • A Complete Time Domain Model of the Induction Motor for Efficiency Evaluation

    Page(s): 68 - 76
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    The saturation of mutual and leakage inductances as well as the eddy currents effects are taken into account to represent an almost complete model of the induction motor. These effects are not trivial, when the stator voltage and/or frequency changes considerably. Therefore, the model is suitable for the motor performance studies under nonsinusoidal voltage waveform supplies. The effects of eddy currents are represented by a simple double cage model equivalent to the deep bar cage. A practical method for finding the double cage parameters is outlined and the results obtained were used in the simulation. The accuracy of the model is emphasized by comparing the simulation results with test results of the stator inrush current during starting under no-load conditions. The model is used for calculating the induction motor losses in the time domain, when the motor is fed from nonsinusoidal voltage waveform supplies. Samples of the obtained results from different voltage waveforms are given together with that of a pure sinusoidal voltage supply for comparison. View full abstract»

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  • Small Signals, Large Signals, and Saturation in Generator Modeling

    Page(s): 94 - 102
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    Test and analytic results from recent EPRI-sponsored programs are organized to explain insights into generator modeling. It is shown how small-signal tests and analysis are related to the nonlinear incremental properties of rotor iron. Changes in rotor circuit topology caused by rotation are identified. The large-signal response of rotor circuits is differentiated from the small-signal response. These effects, customarily lumped under the term ``saturation,'' are separated and differentiated. View full abstract»

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  • Cross-Saturation in Smooth-Air-Gap Electrical Machines

    Page(s): 103 - 112
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    A detailed analysis of the phenomenon of cross-saturation is presented and it is shown that in a smooth-air-gap quadrature-phase machine this phenomenon is similar to the phenomenon of the demagnetizing effect of cross-magnetizing armature reaction in a d.c. machine. In a quadrature-phase smooth-air-gap machine the resultant air-gap flux density distribution is decreased over one half of the pole-pitch and is increased under the other half of the pole-pitch and due to saturation the decrease is greater than the increase. Thus under saturated conditions, if the resultant m.m.f. distribution is displaced from the magnetic axes of the windings, a change in the quadrature-axis magnetizing current will cause a change of flux linkage in the direct-axis winding and vice versa, a change in the direct-axis magnetizing current will cause a change of flux linkage in the quadrature-axis winding. It is an important result that cross-saturation can also exist if the m.m.f. distributions are assumed to be sinusoidal. A physical derivation of the cross-saturation coupling factor is presented and a test is described which shows the existence of cross-saturation. A theoretical analysis of the experiment gives results which are in good agreement with the experimental results. View full abstract»

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  • Effect of Damper Modelling and the Fault Clearing Process on Response Torque and Stressing of Turbine-Generator Shafts

    Page(s): 113 - 121
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    The paper discusses the effect damper circuit modelling and the current interruption process following clearance of grid network disturbances has on machine transient response. Parameters for a 2-direct-axis and 3-quadrature-axis damper circuit model are given, as are those for lower-order damper model equivalents. Torques obtained following clearance of typical L-L-L and L-L non-ground system disturbances at fault current zeros or by simultaneous interruption for detailed and reduced damper models are illustrated. Further, the effect damper circuit modelling has on peak torque response following clearance of supply network disturbances at fault current zeros, sustained L-L-L and L-L stator terminals short-circuits and worst-case malsynchronisation is depicted. View full abstract»

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  • Measured Propagation of Surges in the Winding of a Large A-C Motor

    Page(s): 122 - 129
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    This paper presents the results of impulse tests performed at Ontario Hydro on a portion of a motor winding. The objective of these EPRI funded tests was to determine the wave propagation properties of the motor coils. In all cases, surge voltages were applied to a portion of the winding and the transient voltages, which appear at various points along the portion, were measured. Based on these measurements, conclusions are derived concerning the modes and speeds of surge propagation along the coils of the motor. The results should be of help to engineers and researches concerned with turn insulation strength and surge protection of large A-C motors. The presented data can be used as an aid in the development and calibration of wave propagation models needed for computation of electromagnetic transients in the windings of rotating machines. View full abstract»

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  • Risk of Winding Insulation Breakdown in Large AC Motors Caused by Steep Switching Surges Part 1 Computed Switching Surges

    Page(s): 130 - 139
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    The research reported here and sponsored by the Electric Power Research Institute was initiated to demonstrate the applicability and use of the finite element method for probabilistic assessment of the risk of turn insulation breakdown in large AC motors. Computer models were developed for computation of the electromagnetic transients in the AC motor windings. Mathematical models were developed to compute the risk of turn insulation breakdown. The application of the proposed approach was demonstrated for a typical installation. This allowed evaluation of the advantages of using the finite element method in terms of accuracy, efficiency, capability and limitations. It also identified the need for further research to facilitate the use of this risk assessment method by utility engineers. View full abstract»

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  • The Effect of Hysteretic Damping on Turbogenerator Shaft Torsional Oscillations

    Page(s): 152 - 160
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    Electromechanical interaction between an electrical system and turbogenerator units may, in certain circumstances, lead to shaft oscillatory behaviour which has an onerous effect on the life expenditure of the shaft. The rate of decay of the oscillations produced as a result of a system disturbance is determined by both the electrical and mechanical components of damping. Due to the advances made in the modelling of electrical machines over the past fifty years the effect of the electrical component of damping is well understood and easily incorporated into a system model. The mechanical components of damping are known to be variable, but nevertheless are usually represented as constant viscous coefficients in the shaft system equations of motion. The present paper proposes a method for the evaluation of a variable damping coefficient which depends on the property of the shaft material when undergoing high stress cyclic variations. The effect of this term is to more rapidly reduce the high torque oscillations and reduce low torque oscillations less rapidly. This effect has been observed in practice and hitherto not predicted from simulation studies. The investigation relies on previous work when taking account of the effects of various steam conditions. Emphasis is placed on the derivation of a shaft model which includes equivalent variable viscous damping and representative results are collected to show the effect of this important parameter on the pattern of derived shaft torques based on a representative 600 MW turbo-generator. View full abstract»

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  • A Passive Shunt Device to Suppress Torsional Interactions in Synchronous Generators

    Page(s): 161 - 168
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    Torsional interactions encountered with series compensated transmission lines are due to the negative damping effect of subsynchronous frequency currents induced by rotor oscillations. Methods of controlling these currents have appeared in the literature, however, this paper offers an alternative scheme based on enhancing the supersynchronous currents associated with positive damping. This results in cancellation of the negative electrical damping at the mechanical resonant frequency. The countermeasure consists of a passive shunt device connected at the generator terminals and tuned to the proper resonant frequency. The operating principle and design considerations are discussed and the effectiveness of the scheme is demonstrated. View full abstract»

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  • Contributions to the Steady State Analysis of Wind-Turbine Driver Self-Excited Induction Generators

    Page(s): 169 - 176
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    The paper makes the following three contributions: First, it presents a digital computer method of predicting the steady state performance of a self-excited induction generator for given spped, capacitance and load conditions along with results of validation studies on a laboratory machine. Secondly, a procedure is presented to check whether the operating point of a given uncontrolled wind-turbine driven self-excited induction generator set on load is a satisfactory point. Details of the resulting capability chart are discussed by application to a specific case. Finally, an experimental method of simulating wind-turbine drive characteristics is presented along with details of implementation of a laboratory set-up involving a d.c. dynamometer coupled to an induction generator. View full abstract»

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  • Nonlinear Vector Potential Formulation and Experimental Verification of Newton-Raphson Solution of Three Dimensional Magnetostatic Fields in Electrical Devices

    Page(s): 177 - 185
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    An iterative technique, based on magnetic vector potential formulation and the Newton-Raphson method, for the determination of the three dimensional magnetostatic field distributions in electrical devices is given. The proper degrees of magnetic saturation in the various materials within a given volume under consideration are obtained by repeated evaluation of the reluctivities in that volume, using a cubic spline representation of the B-H magnetization characteristics of composite materials (laminations). The formulation has been applied to a practical example of determining the field in and around a shell type 1.5 kva single phase transformer. The convergence and implementation characteristics of the developed method are given in this paper which show a saving of about 34% in CPU solution time in comparison with previously published methods. Experimental verification is given in terms of a comparison between computed and experimentally obtained values of flux densities surrounding the transformer core and winding, under heavily saturated conditions. Excellent agreement between test and calculated flux densities was achieved. This method is thus quite applicable to the solution of a wide class of three dimensional magnetostatic field problems associated with electrical apparatus. View full abstract»

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Aims & Scope

The IEEE Transactions on Energy Conversion includes in its venue the research, development, design, application, construction, installation, operation, analysis and control of electric power generating and energy storage equipment (along with conventional, cogeneration, nuclear, distributed or renewable sources, central station and grid connection). The scope also includes electromechanical energy conversion, electric machinery, devices, systems and facilities for the safe, reliable, and economic generation and utilization of electrical energy for general industrial, commercial, public, and domestic consumption of electrical energy.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Juri Jatskevich
University of British Columbia