In the circulating current type cycloconverter system, a harmonic resonance is induced by the inductance of the utility power system, shunt capacitors, and the cycloconverter. This harmonic resonance has an influence on the operation of the cycloconverter. This paper describes the analysis of this harmonic resonance phenomenon. Namely, the conversion process for the harmonics in the cycloconverter is analyzed, and the relation between the harmonic resonance phenomenon and the respective capacities of the utility power system and the shunt capacitors is examined based on results of the analyses. Moreover the analyses are confirmed by the field test.

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As the method of deterioration diagnosis for 6kV class XLPE cables, there exist leakage current method, tan δ method, etc. It is strongly desired to establish a complex judgment technology with high accuracy using these methods, and now various methods for it are being proposed. However, most of these methods for complex judgment are only to make a comprehensive judgment combining judgment results of “good” or “not good” obtained by diagnostic methods, and there have not been any materialized methods in practical use, which can comprehensively handle the values measured by diagnostic methods. Now, the author and others have contrived a method to improve the accuracy of deterioration diagnosis based on the statistical way, confirmed the expected effects being verified with the actual data, and then have obtained the prospects for the practical use. This method is composed of the following three techniques, and the accuracy of deterioration diagnosis can be largely improved by the application of these techniques. These three techniques are (1) application of logarithmichyperbolic regression equation, (2) application of analytical method of covariance for multiple regression equation, and (3) multiple correlation analysis with single correlation data

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A Static Var Generator (SVG) based on a self-commutated inverter using GTO thyristors has been newly developed. The size of the SVG used for improving power system stability will be as large as around 100 MVA. The technical subjects to be solved for developing such a large SVG are summarized as follows:
(1) Compact design
(2) Harmonic elimination by means of multiple transformer
(3) Large inverter with series concection of GTO thyristors
This paper describes the solutions to these subjects, especially the application of large number of multi-pulse connection and series connection of GTO thyristors, including the analysis of the basic performance of SVG and the multiple transformer. The test results of a 12-pulse partial model (8 MVA) and a 48-pulse miniaturized model prove the solutions proposed in this paper to be effective and reasonable.

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Shunt passive filters, which are connected in parallel to harmonic-producing loads, have been widely used for harmonics suppression in power systems because of low costs and high efficiency, although they have inherent problems such as series and parallel resonance. On the other hand, shunt active filters, which are also placed in parallel, have such an inherent problem as initial and running costs are high, compared with those of shunt passive filters. To solve these inherent problems in shunt passive and shunt active filters, the authors have proposed a combined system of a shunt passive filter and a small rated series active filter.
The purpose of this paper is to reduce the required rating of the series active filter, considering a practical application of the combined power filter to harmonic compensation for large capacity thyristor converters. The points are summarized as follows:
(1) The required rating of the series active filter can be reduced less than one-tenth by connecting a series resonant circuit in parallel to the secondary of current transformer.
(2) It is clarified theoretically and verified experimentally that compensation characteristics of the new combined system are equivalent to those of the already proposed system with no series resonant circuit.

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The magnetic flux inside a synchronous generator is regarded as a characteristic that dominates a generator operation. This paper develops a simple model of a synchronous generator by the use of which it is possible to estimate a air-gap flux as well as electrical characteristics easily. The air-gap flux density can be related with a permeance and a magneto-motive force (mmf) along its magnetic path by the Ampere's laws. These relations are adopted in this paper.
We practically estimate the distribution of the permeance along the air-gap and the mmf profiles of the stator and the rotor of 6kVA scaled-down tested synchronous generator. By the use of these estimated profiles, the relations among the air-gap flux, field current and armature current are represented by a linear equation system. Consequently, the static electrical and magnetic characteristics of a synchronous generator can be estimated by giving only field exciting voltage and load impedance. The distributions of the air-gap flux density and waveforms of the field and armature currents are simulated for various unbalanced-load conditions. The simulated results are well agreed with experimental ones not only for fundamental components but also for higher harmonic components. Therefore, our developed method based on the permeance profile is available to calculate the static characteristics of synchronous generators.

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A linear pulse motor (LPM) has been examined, for application to actuators of floppy disk drives, hard disk drives, printers, etc. A permanent magnet (PM) type LPM is superior in thrust force to other variable reluctance (VR) type LPMs and hybrid (HB) type LPMs. However it is difficult to calculate performance of the PM type LPM, because the electromagnetic fields in an air gap between a magnet and the teeth have to be estimated with a finite element method.
We propose a simple method, in which magnetic paths in the air gap are assumed to be straight lines and circles, to estimate the magnetic flux in the air gap and an iron core with winding coils, thrust force and inductance. This method is shown useful for estimating the thrust force of PM type LPMs, especially assuming the width of the magnet pole to be narrower than the real one and when compensating magnetic paths with a leakage magnetic path.

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The control strategy based on fuzzy logic is proposed for levelling the load power fluctuation and compensating the reactive power by using the superconducting magnetic energy storage (SMES) equipped near to the consumer. Then, its control effects are discussed by simulation. The obtained results are summarized as follows.
(1) The conditions with respect to the levelling of the active power in the source line and the energy stored in the SMES are introduced. Then, the production rules on these conditions are constructed.
(2) The estimation value L_D of levelling the active power in the source line is proposed in addition to the estimation value υ of following the sustained component.
(3) Provided that the base of the triangle in the menbership function is set to 1.05 for the load power fluctuation investigated, the most preferable result can be obtained when the heights of triange are 0.01 and 0.6 in the rule 1 and the rule 2, respectively.
(4) Comparing with the control results by using the estimation function, the estimation value υ with the fuzzy control is less than that with the estimation function regardless of the capacity of the SMES. Therefore, it is clarified that the levelling of load power fluctuation can be achieved by the fuzzy control better than by the estimation function.

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Recently, in the industrial application, the direct drive method with linear motor has been introduced and contributed practical use. From this view point, we designed the cylindrical linear pulse motor (“CLPM”)for OA machines, which mover envelopped the stator on purpose to cancel the normal force.
The basic structure of CLPM has two excitation windings on the stator. They are wound A and B-phase, alternately. The mover has arrangement of permanent magnets on the inner surface of the cylindrical iron.
First, we calculate the flux density distribution in the air gap at the CLPM by Finite Element Method. And by mean of Maxwell's stress law with above flux density, we analyze the thrust force vs. displacement.
Second, we got harmonic components of static thrust characteristics of CLPM.
Finally, we design a new method which excitation currents cancel harmonics included thrust characteristics. This method realizes the high positioning accuracy for every Linear pulse motor.

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