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An analytical method to determine the no-load and armature reaction magnetic fields of a single-sided, axial flux permanent-magnet synchronous generator without armature core is presented. Laplace's equation is solved in the rectangular coordinate system to give the scalar magnetic potentials, using a Fourier series method. For computation of the armature reaction field, a multi-current-sheet model is employed in order to account for the distributed nature of armature conductors in the axial direction. Finite element analysis and experimental results on a prototype machine are presented for verifying the accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a unique axial-flux permanent-magnet synchronous generator (AFPMSG), which is suitable for both vertical-axis and horizontal-axis wind turbine generation systems. An outer-rotor design facilitates direct coupling of the generator to the wind turbine, while a coreless armature eliminates the magnetic pull between the stationary and moving parts. The design and construction features of the AFPMSG are reviewed. The flux-density distribution is studied, with the aid of a finite element software package, in order to predict the generated e.m.f. wave-form. The performance equations of the AFPMSG are derived, and the condition for maximum efficiency is deduced, for both constant-speed and variable-speed operations. The experimental results, in general, confirm the theory developed. [ABSTRACT FROM AUTHOR]

This paper presents a transient analysis of a three-phase induction motor with the Smith connection using a time-stepping, coupled circuit, two-dimensional finite element method. A systematic approach enables the stator and rotor circuit equations to be coupled to the field equations. The Maxwell stress method is used to compute the air gap torque that is required for solving the equation of motion. Various cases of motor run-up transients are investigated. Where possible, the computed results are verified by experiments on a small induction machine. [ABSTRACT FROM AUTHOR]

The performance analysis of a stand-alone permanent-magnet synchronous generator with inset rotor using a coupled-circuit, time-stepping, two-dimensional finite-element method is described. The direct-coupled field-circuit method enables the instantaneous values of the field and circuit variables to be solved simultaneously, without having to evaluate the synchronous reactances and the load angle. Magnetic saturation is accounted for by considering the flux densities in the elements of the field solution region. Besides the load characteristics, the coupled field-circuit solution also yields other useful machine information including the flux plots, components of the air-gap flux density, and the waveforms of voltages and currents. The flux plots obtained clearly demonstrate the effect of armature current on the interpolar flux that helps to improve the voltage regulation. Good agreement between the computed and experimental results has been obtained on a 2.5 kVA prototype generator. [ABSTRACT FROM AUTHOR]

By using two capacitances and a current injection transformer, a three-phase induction generator can operate with good phase balance and line power factor while delivering power to a sing-phase power grid. This paper presents a systematic analysis on this novel induction generator configuration. The solution of the system's inspection equations using the method of symmetrical components enables the steady-state generator performance at any speed to be computed. The conditions for achieving perfect phase balance are deduced from the phasor diagram. It is shown that the capacitances that result In perfect phase balance depend on the generator admittance, power factor angle, as well as the turns ratio of the current injection transformer. Where possible, the computed results are verified by experiments conducted on a 2-kW induction machine. An experimental investigation on the system waveforms and harmonics is also carried out. [ABSTRACT FROM AUTHOR]

This paper presents the analysis and performance of a three-phase ac generator with an inset, neodymium- iron-boron (NdFeB) permanent-magnet (PM) rotor. Such a rotor construction gives rise to an inverse saliency effect (i.e., the direct-axis synchronous reactance is less than the quadrature-axis synchronous reactance). This feature results in an improvement in the voltage regulation characteristics when the generator supplies an isolated, unity-power-factor load. By solving the equations derived from the two-axis theory, it is found that there exists, in general, two values of load current at which zero voltage regulation is obtained. The relationship between armature resistance, inverse saliency ratio, and the operating speed to give zero voltage regulation is investigated. The finite-element method (FEM) is used for computing the pertinent. generator parameters for performance evaluation, namely the no-load voltage and the synchronous reactances. Flux plots are presented to confirm the origin of inverse saliency in the inset PM rotor. The theoretical analysis is validated by experiments carried out on a 2.5-kVA prototype generator. [ABSTRACT FROM AUTHOR]

This paper presents the operating principle and steady-state analysis of a novel excitation scheme for a stand-alone three-phase induction generator that supplies single-phase loads. The phase windings and excitation capacitances are arranged in the form of the Smith connection and the excitation scheme is referred to as the SMSEIG. In addition to providing the reactive power for self-excitation, the capacitances also act as phase balancers. With this novel excitation scheme, isolated single-phase loads can be supplied with good phase balance in the induction machine, resulting in high efficiency, large power output, and quiet machine operation. Performance analysis is based on the method of symmetrical components, from which the input impedance of the generator can be determined. Numerical solution of a simplified equivalent circuit for the machine variables, namely the excitation frequency and magnetizing reactance, enables the generator performance to be evaluated for any load and speed. With the aid of a phasor diagram, the conditions for achieving perfect phase balance are deduced and a method to compute the capacitances required is developed. Experimental investigations on a 2.2-kW induction machine confirm the feasibility of the SMSEIG. [ABSTRACT FROM AUTHOR]

Presents a study which showed that the factors affecting the operating region of a digital distance relay is the power flow. Impact of advances in the microprocessor technology and communication systems to digital distance relaying; Application of artificial neural network in adaptive distance relay; Conclusions.

This letter gives the correction to a few mistakes in the illustrations of a paper published by the authors in the IEEE TRANSACTIONS ON ENERGY CONVERSION. [ABSTRACT FROM AUTHOR]

The magnet field in a new form of transverse- and axial-flux permanent-magnet synchronous generator is studied. In this novel machine configuration, the main flux flows in the transverse direction as the rotation. The flux density distribution is analyzed using a 3-D finite-element method (3-D FEM). Details of field computation, including the convergence criterion, are explained. Experimental flux density measurements are in good agreement with the computed results. Using a time-stepping technique, the output voltage and current waveforms of the generator are also computed and the accuracy is confirmed by load tests. [ABSTRACT FROM PUBLISHER]

For the first time, this paper presents field computation results and performance of an axial-flux permanent magnet synchronous generator (AFPMSG) based on a time-stepping, 3-D finite-element analysis (3-D FEA). The prototype generator studied has a ferromagnetic outer rotor frame and a totally enclosed design, while a coreless stator armature configuration is used. Based on the machine geometry, a 3-D FEA model is developed in order to determine the principal field components. The flux in the rotor back plate and the transverse flux through the ferromagnetic spacer, which is part of the rotor frame, can both be predicted. A time-stepping, coupled field-circuit approach enables the waveforms and load characteristics of the AFPMSG to be obtained accurately. The computed results are validated by experiments on the prototype generator. [ABSTRACT FROM AUTHOR]

The analysis and performance of a permanent-magnet synchronous generator (PMSG) supplying an isolated load at constant speed is presented. The two-axis model is used for computation of the load characteristics of the PMSG and to study voltage compensation using shunt-connected capacitance. For a more comprehensive study, a time-stepping, coupled field-circuit analysis is developed using a two-dimensional finite element package. The time-stepping finite element analysis is applied to study the steady-state and transient performance of the PMSG when supplying an isolated resistive load. With appropriate modification of the external circuit model, the steady-state performance of a PMSG which supplies a bridge rectifier load is also studied. Voltage regulation characteristics, waveforms and harmonics are investigated. The computed results are verified by experiments on a 2.5 kW PMSG. [ABSTRACT FROM AUTHOR]

The detection of insulators contamination is difficult in power systems because many factors can influence the pollution. The contamination condition of insulators is usually estimated by detecting the root mean square (r.m.s) of surface leakage current via online-monitoring system. It ignores the influence of environmental factors, such as temperature, humidity, etc. As these factors are fuzzy-characterized, a new method based on Fuzzy Neural Network (FNN) is proposed to improve traditional insulation contamination detection. The renewed structure of FNN is put forward. The evaluation of contamination severity of insulators is achieved through FNN, which are trained by the field samples. The results prove the validity of the method proposed in the paper and can be used to eliminate the insulator from flashover fault and improve the condition-based maintenance (CBM). [ABSTRACT FROM AUTHOR]

A rapid on-line frequency estimation algorithm with the help of non-linearity is presented. A full-wave rectification of the raw signal is carried out such that the fundamental frequency is doubled. The rectified signal is filtered and the signal frequency is extracted based on the filtered fundamental component and second order harmonics. Simulation example and real measurement are included to demonstrate the effectiveness of the algorithm. [ABSTRACT FROM AUTHOR]

The analysis and performance of a three-phase synchronous generator with an inset permanent-magnet rotor is presented. Relevant performance equations are developed based on the two-axis model. The conditions for achieving zero voltage regulation,extremum points in the load characteristic and maximum power output, are deduced analytically. The finite-element method is used for computing the magnetic-field distribution, from which the effects of saturation on the synchronous reactances are quantified. Experiments performed on a 2.5 kVA prototype generator show that the saturated two-axis model gives a more accurate prediction of the load characteristics of the generator. [ABSTRACT FROM AUTHOR]

By varying the effective rotor resistance of a self-excited slip-ring induction generator (SESRIG), the magnitude and frequency of the output voltage can be controlled over a wide speed range. A steady-state analysis based on a normalized equivalent circuit enables the control characteristics to be deduced. For a given stator load impedance, both the frequency and the voltage can be maintained constant as the speed is varied, without changing the excitation capacitance. When the stator load is variable, simultaneous voltage and frequency control requires the excitation capacitance to be changed as the rotor resistance is varied. Experiments performed on a 1,8-kW laboratory machine confirm the feasibility of the method of control. Practical implementation of a closed-loop control scheme for an SESRIG using chopper-controlled rotor resistance is also discussed. With a properly tuned proportional-plus-integral (PI) controller, satisfactory dynamic performance of the SESRIG is obtained. The proposed scheme may be used in a low-cost variable-speed wind energy system for prodding good-quality electric power to remote regions. [ABSTRACT FROM AUTHOR]