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Energy Conversion, IEEE Transactions on

Issue 2 • Date Jun 1990

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Displaying Results 1 - 25 of 27
  • Electromechanical spring stiffness from the small perturbation linearized equations of generalized machine theory

    Page(s): 374 - 379
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    The authors derive the static electromechanical spring stiffness coefficient of the class of balanced polyphase electric machines which are amenable to the generalized machine reference-frame transformation. The stiffness coefficient derived from the torque equation of the original unprimed frame expressed in the linearized small-perturbation form is given. The spring stiffness, which is physically present but suppressed in the reference-frame transformation, is then modeled and can be used effectively for transient analysis and the analysis of the dynamics of motion control systems. A procedure for the calculation of the stiffness coefficient is described and the electromechanical spring stiffness coefficients of synchronous machines and the induction machine are derived View full abstract»

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  • Improved generator temperature monitoring for hydroelectric power plants

    Page(s): 259 - 264
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    A fully automated temperature monitoring system for hydroelectric generators and pumps is described. The system collects, archives, and analyzes the data for the operator, and generates reports defined by the operator. Design considerations as well as hardware, software, and data configurations are presented. Installation and operation are discussed View full abstract»

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  • Noiseless variable-speed squirrel-cage induction motor

    Page(s): 380 - 385
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    A variable-speed squirrel-cage induction motor is proposed. It is made up of a squirrel-cage rotor and two stators, one of which can be turned for speed control. The proposed motor has the following special features: (1) The range of speed control is extremely wide and the motoring operation is almost constant-torque under constant supply source voltage and frequency. (2) No special source such as an inverter is required; (3) Smooth operation from starting to the rated speed can be expected without any special starter because of suppressed starting current and large starting torque. The results of a theoretical analysis and experiments on a test motor are given, and the characteristics of the motor are discussed View full abstract»

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  • Comparison of the nature of torque production in reluctance and induction motors

    Page(s): 304 - 309
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    The nature of torque production is different in reluctance and inductance motors. One significant difference occurs in a reluctance motor that has nonsalient stator punching and a salient motor. When the flux per pole is small in such a motor, the torque can still be high, as long as the rate of energy change with respect to the rotor angular displacement at the rotor pole fronts and pole ends is high. A theoretical foundation to improve the torque capability of reluctance motors is provided. Effects of saturation and stray-load loss are also studied. Experimental results show agreement with theoretical conclusions View full abstract»

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  • Degradation of turn insulation in motor coils under repetitive surges

    Page(s): 320 - 326
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    Degradation of interturn insulation caused by repetitive surges is studied for coils in three motors stators. In each stator, the coils are isolated and divided into several groups. Breakdown voltages of coils in one group are measured for 0.1 μs risetime impulses and the average breakdown voltage of these unaged coils is determined. Coils in the other groups are first subjected to a number (1000 to 8000) of surges with magnitudes of 3.0 to 7.8 pu, and then the impulse breakdown voltages for these aged coils are measured and compared with those for the unaged coils. The results of the measurements on two stators showed no evidence of degradation of turn insulation by surges. There is an indication of surge aging of the turn insulation for one stator. Surge magnitudes capable of causing detectable aging of turn insulation appear to be higher than those likely to occur at normally operating utility motors. The existence of a threshold value of surge magnitude required to produce aging effects is a possible hypothesis View full abstract»

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  • Determination of starting current in three-phase induction motors

    Page(s): 386 - 392
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    The author reviews the existing conversion methods which determine the starting current in three-phase induction motors and points out their weaknesses. A theoretical base is found for the determination of starting current, and an accurate method called the regression estimate method is proposed View full abstract»

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  • Photovoltaic operation and maintenance evaluation

    Page(s): 279 - 283
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    An Electric Power Research Institute (EPRI) sponsored evaluation of the operation and maintenance (O&M) experience at seven selected photovoltaic installations in the United States is presented. The presentation of the actual O&M costs experienced by the seven sites, documentation of the largest problem areas, identification of failure causes, and projections of O&M costs for future installations are included View full abstract»

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  • Interface requirements of a large hydroelectric power plant with its regional load dispatch office

    Page(s): 299 - 303
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    The real-time interface requirements of a large hydroelectric power plant with its regional load dispatch office are described. The operative arrangement, interfacing functions, annual and weekly generation schedule, and unit commitment are discussed. Automatic generation control, automatic bus voltage, river flow control, and operating conditions are discussed. All the functions were implemented for the Guri Hydroelectric Project in Venezuela, with total generating capacity of 10000 MW. Operation management functions are all handled by the Guri Computer Control System View full abstract»

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  • Field tests and operation of a duplicate multiprocessor-based governor for water turbine and its further development

    Page(s): 225 - 231
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    The details are given of the hardware and software and the field test results for a duplicate microprocessor-based governor (DμPG). An evaluation of the financial benefits with examples from the 11 DμPGs operating at seven different hydro-power plants in China is given. A proposal is presented for a new DμPG with a control strategy based on intelligent self-improvement View full abstract»

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  • Improved models for the simulation of deep bar induction motors

    Page(s): 393 - 400
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    Four lumped-parameter circuits to be used in modeling the deep bar effects in rotors of induction motors are presented. Traditionally, the lumped-parameter circuit is obtained by dividing the rotor bar into equal sections; an improvement is proposed which divides the bar unequally to have a greater number of smaller sections at the top of the bar where the current will flow under transient conditions. A complex model is shown to be more accurate than other lumped-parameter models across a wide range of frequencies View full abstract»

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  • The New England electric photovoltaic systems research and demonstration project

    Page(s): 284 - 289
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    The design, installation, and operation of photovoltaic systems at 30 residences and 8 commercial or institutional sites are described. The correlation between hourly PV production and system daily load profile, the potential impact of PV production on residential customer load, the relationship between PV energy production and cloud cover, and the monthly variation in energy output are discussed View full abstract»

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  • Optimum load matching in direct-coupled photovoltaic power systems-application to resistive loads

    Page(s): 265 - 271
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    The load matching factor is used as a measure for the quality of load matching to a photovoltaic (PV) array. An optimization approach is used to solve the load matching problem with the objective of maximizing the load matching factor, and consequently the PV output energy. This approach is then applied to resistive loads (with and without an internal EMF) connected to the array. Results show that optimum matching can be achieved by carefully selecting the array parameters with respect to the load parameters. The temperature of the array has little effect on the optimum matching factor. However, the optimum matching parameters are greatly affected by the array temperature. A maximum power tracker may not be achieved View full abstract»

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  • A comparison of induction motor models for bus transfer studies

    Page(s): 310 - 319
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    A study was undertaken to determine if improved accuracy can be obtained using different induction motor models for bus transfer simulations where the loads have low inertias. Bus transfer simulations are presented using five different models. Based on a comparison of these simulations, separate motor models for the disconnect period, the period immediately after reenergization, and the longer time period during which bus voltage and motor speeds are restored are recommended View full abstract»

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  • Operational performance of generator condition monitors: comparison of heated and unheated ion chambers

    Page(s): 344 - 349
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    Generator condition monitors (GCMs) are evaluated under field conditions in a 550 MW turbogenerator. Small 100 W resistors coated with insulating paints and varnishes are mounted inside the generator to simulate overheating. The GCM responds very rapidly to an overheating event, typically within two minutes, even for hot spots as small as 10 cm2. Similarly, the aerosols produced on overheating are extremely short-lived, decaying within two to three minutes after overheating is discontinued. Use of heated ion chambers is found to desensitize the GCM regardless of the nature of the overheated insulation and in some cases prevents the GCM from reaching the 50% preset alarm level commonly used on GCMs. Use of heated ion chambers is therefore generally not recommended except where severe oil mist problems may exist View full abstract»

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  • Second order hydraulic turbine models for multimachine stability studies

    Page(s): 239 - 244
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    An approximation of the exact hydraulic turbine transfer function which is particularly suitable for stability calculations in a multimachine power system is presented. This approximation is made with a second-order transfer function, the coefficients of which are estimated so that it resembles as closely as possible the dynamics of the actual hydraulic turbine in the frequency range of the electromechanical oscillations between the synchronous machines of the system. The method is applied to a realistic multimachine model of the Hellenic Interconnected System and the improvement in accuracy over the traditional first-order hydro turbine model is found to be significant View full abstract»

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  • Performance analysis of permanent magnet synchronous motors. I. Dynamic performance

    Page(s): 366 - 373
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    The dynamic performance of permanent magnet (PM) synchronous motors using damping and synchronizing torques is analyzed. A numerical algorithm is applied to obtain these torque components using a time-domain analysis of nonlinear systems. The effects of all electrical parameters are examined and the optimum values which give maximum internal damping are defined. It is demonstrated that the choice of the optimum values of these parameters results in well-damped oscillations with improved dynamical performance following load changes View full abstract»

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  • Performance model of molten carbonate fuel cell

    Page(s): 252 - 258
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    A performance model of a molten carbonate fuel cell (MCFC), an electrochemical energy conversion device for electric power generation, is discussed. The presumptive ability of the MCFC model is improved and the impact of MCFC characteristics in fuel cell system simulations is investigated. Basic data are obtained experimentally by single-cell tests. A correlation formula based on the experimental data is derived for the cell voltage and the oxygen and carbon dioxide partial pressures. Three types of MCFC systems are compared. With regard to fuel utilization, system characteristics using the proposed correlation are very similar to those obtained using a previous model. However, the amount of decrease predicted by the proposed model with respect to system efficiency is larger than that obtained by the previous model at high air utilization View full abstract»

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  • Harmonics and core losses of permanent magnet DC motors controlled by chopper circuits

    Page(s): 408 - 414
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    The impact of chopper control on armature current harmonics and core losses of permanent-magnet DC motors is analyzed. A computer-aided two-dimensional finite-element method is used to analyze the magnetic field and obtain the nonlinear parameters of the machine. The armature current waveforms are predicted from the machine system network analysis at different chopping frequencies and decomposed into their AC and DC components. These currents with their ripple contents are further used in the field analysis to compute the core losses of a 1.2 hp permanent-magnet DC motor at different operating conditions. In addition to the numerical analysis, supporting experimental work was carried out for verification of some of the results. It is found that armature current harmonics can lead to significant increases in core losses View full abstract»

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  • Transient behaviour and self-excitation of wind-driven induction generator after its disconnection from the power grid

    Page(s): 272 - 278
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    The transient behavior of a wind-driven induction generator after its disconnection from the power grid is investigated. Measurements on an experimental arrangement, followed by theoretical analysis, show that self-excitation always occurs when there is torque and the generator is compensated. Over a wide range of compensation power, the self-excitation voltage does not change significantly. Suggestions for protection against self-excitation are made View full abstract»

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  • Design analysis of capacitor-start, capacitor-run single-phase induction motors

    Page(s): 327 - 336
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    Capacitor-start, capacitor-run single-phase induction motors are analyzed by means of rotating field theory using the method of symmetrical components. The approach is based on the current ratio γ, relating the backward and forward rotating components of the main and auxiliary-phase winding currents. Since the losses of such a machine are greatly dependent upon the elliptic shape of the rotating field, such an analysis in terms of γ will be of value for any efficiency optimization. The dependency of the efficiency on the run capacitor's capacitance is investigated. Since the parameters of the equivalent circuit are slip, temperature, and saturation-dependent, a computer program is developed which determines in an iterative manner the performance of such machines. A large number of tests are performed for a 4-pole, 2 Hp, 115/230 V motor. The experimental data corroborate the calculated characteristics which show that the maximum efficiency is reached for a nonzero but small value of γ View full abstract»

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  • Review of photovoltaic power plant performance and economics

    Page(s): 232 - 238
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    The author reviews the performance, availability, and maintenance for ten photovoltaic plants since 1983. Problems are examined and achievable capacity factors are presented. The cost of photovoltaic electricity is developed as a function of investment cost, maintenance costs, and capacity factor, which in turn is shown to depend upon the site, the plant's availability, and the tracking employed View full abstract»

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  • Optimal estimation of the generalized operational impedances of synchronous machines from short-circuit tests

    Page(s): 401 - 407
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    A nonlinear procedure for estimating the dynamic constants of a synchronous machine from sudden short-circuit data is presented. The machine, which is assumed to be operating in a quasi-linear mode, is modeled by operational impedances of a suitable order. By conferring much greater flexibility in the choice of the number of damper windings in each axis, the proposed method of analyzing short-circuit oscillographs is particularly appropriate when the machine is a solid-rotor turbogenerator. By means of a canonical state variables realization of the machine admittance matrix, the proposed algorithms permits an optimal estimation of the three classical operational impedances in a time-domain framework. It is then possible, by means of a few classical approximations, to deduce algebraically the equivalent circuits of the turbogenerator View full abstract»

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  • First year performance of a 15 kWp amorphous silicon photovoltaic system

    Page(s): 290 - 298
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    A report on a 15 kWp grid-connected photovoltaic system employing thin-film amorphous silicon modules is presented. The system performance monitoring and diagnostics were conducted for nearly a year of operation to determine the array efficiency, array power degradation, and system reliability. The system installation, description, and reliability are reported. The data show that after one year the power output of the photovoltaic array has degraded by about 16% of its initial value and the array peak power efficiency is 4.5% View full abstract»

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  • A generalized computer-aided formulation for the dynamic and steady state analysis of induction machine inverter drive systems

    Page(s): 337 - 343
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    A generalized formulation for the computer-aided analysis of induction machine drives including feedback controls is presented. A simple circuit model for the induction machine is developed to enhance the conventional drive formulation. This model eliminates a general difficulty encountered in the automatic formulation of machine dq -terminal constraints imposed by the drive operations. An efficient algorithm is proposed using a simple nodal approach for automatic formulation of power electronic circuits. This algorithm, combined with the proposed machine circuit model, can easily be used to simulate an arbitrarily configured drive system including the effects of control dynamics. A pulse-width-modulated current-source-inverter drive system is employed to demonstrate the efficiency of the proposed formulation. The dynamic and steady-state performance of this drive system including an effective harmonic control are simulated. The simulated results are experimentally verified View full abstract»

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  • A computer program to predict the performance of slip energy recovery induction motor drives

    Page(s): 357 - 365
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    Details are provided, in the form of a flowchart, to permit the reconstruction of a computer program to predict the transient and steady-state performance of slip energy recovery induction motor (IM) drives. Slip energy recovery IM drives are different from most other drives in that the inverter is generally connected only after the machine has reached a predetermined speed. The initial conditions of the inverter are therefore nonzero and difficult to obtain. Three techniques that can be used to calculate the initial conditions are discussed. Theoretical predictions are supported by practical results 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