Electromagnetic analysis coupled with motion for high‐speed circuit breakers of eddy current repulsion using the tableau approach

Electromagnetic field analysis coupled with motion using the tableau approach has been applied to high‐speed circuit breakers of eddy current repulsion mechanisms. This breaker has an opening time of 1 ms and break time less than 1 cycle (20 ms). The driving part of the breaker is composed of electromagnetic repulsion mechanisms and disk springs with nonlinear characteristics. The mechanisms are composed of two fixed coils and one repulsion plate. A numeric experiment has been applied to investigate the dynamic behavior of the electromagnetic repulsion mechanism using the equivalent circuit method. Calculation results were in good agreement with both measurement results and calculation results by FEM on an experimental model. In addition, repulsive forces depending on material conductivities have been researched. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 8–16, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20149     

General circuit equation formulation method for simulation of a power electronic system

This paper proposes a general circuit equation formulation method by generalizing the conventional modified nodal analysis (MNA) method. The method consists of two equation types; one is conversation equations which express a conservation law in each physical system like Kirchhoff's law for an electrical system and the other is constraint condition equations, for example, signal flow relations in a control system. Therefore it is possible to analyze a mixed physical system generally by formulating equations simultaneously with node variables of systems and necessary constraint equations. MNA has special features such that it can express contributions of each element or component to the equations simply and clearly by a so‐called stamp. This paper derives how to express the contributions and get a stamp for the equations. A stamp is flexible and not unique and dependent on purposes. It is possible to select a stamp for each element to be compatible with ones by the tableau method. A prototype simulation program is developed and validated for four application examples which are selected to show how the proposed method works. It is possible to simulate a power electronic system generally by developing such a simulator which can handle general stamps from input data information flexibly. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 58–65, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20048     

Development of a high‐speed electromagnetic repulsion mechanism for high‐voltage vacuum circuit breakers

This paper presents a design and testing of a new high‐speed electromagnetic driving mechanism for a high‐voltage vacuum circuit breaker (VCB). This mechanism is based on a high‐speed electromagnetic repulsion and a permanent magnet spring (PMS). This PMS is introduced instead of the conventional disk spring due to its low spring energy and more suitable force characteristics for VCB application. The PMS has been optimally designed by the 3D nonlinear finite‐elements magnetic field analysis and investigated its internal friction and eddy‐current effect. Furthermore, we calculated the dynamic of this mechanism coupling with the electromagnetic field and circuit analysis, in order to satisfy the operating characteristics—contact velocity, response time, and so on, required for the high‐speed VCB. A prototype VCB, which was built based on the above analysis, shows sufficient operating performance. Finally, the short circuit interruption tests were carried out with this prototype breaker, and we have been able to verify its satisfying performance. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 34–40, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20398     

A novel method of output voltage stabilization with respect to load current variation in noncontact energy transfer

This paper examines a noncontact energy transfer system which can stabilize the load voltage with no‐feedback control. A detachable transformer used in the system has a leakage inductance. Therefore, load voltage decreases greatly in proportion to load current. A feedback control circuit of the noncontact energy transfer system is more complicated than that of the contact energy transfer system. Consequently, even if without feedback control, a noncontact energy transfer system which can maintain the approximate fixed load voltage is required. The authors have analyzed the load voltage characteristic in detail and researched the mechanism, and found a novel method which minimizes the load voltage drop rate by using optimized capacitance value of two resonant circuits. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(2): 63–74, 2005; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20032     

A novel voltage clamped snubber circuit topology suitable for a multilevel inverter with lowered power loss performance

This paper presents a novel prototype of lowered loss snubber circuit topology suitable for multilevel voltage source‐inverters and rectifiers for high‐power applications. The reduced power loss characteristics and voltage capability performances of the proposed voltage clamped snubber circuit are evaluated relative to conventional RCD snubber circuits designed for four‐level voltage‐source inverters using IGBTs on the basis of experimental results. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 70–78, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20015     

Effects of multiple interruptions on post‐arc current,reignition, and lifetime of distribution breaker

The purpose of this investigation is to study the interruption performance of the Molded Case Circuit Breaker (MCCB) currently used for the protection of low‐voltage circuits. It is anticipated that interruptions, especially numerous high‐current interruptions, will degrade interruption performance. In order to investigate the performance change after many interruptions, it is important to understand the interruption characteristics. Multiple‐interruption experiments at large currents were conducted and the phenomena which govern the success or failure of interruption were identified. It was shown that after multiple interruptions a post‐arc current begins to flow and that the duration of the arc is ten to a few hundred microseconds. In order to explore the relationship between the post‐arc current and the degradation of the interruption characteristics, the conditions governing the post‐arc current were investigated experimentally. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 42–49, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10358     

Study of asynchronizing phenomena using generator model with field mutual leakage reactance

This paper describes the effect of mutual leakage reactance in the rotor circuit on the analysis of generator transient characteristics. The authors derive a detailed equivalent circuit model for a 48P‐15,750‐kVA generator, analyze sudden short circuits and asynchronization phenomena of the generator by simulations with an electromagnetic transients program (ATP‐EMTP), and compare the results with experimental data. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 31–40, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20147     

Development of a voltage sag detection method for nonutility generation systems

This paper deals with a new detection method based on three‐phase vector operation for voltage sag. The detection method is applicable to a protection system using a high‐speed interruption system which protects distributed generators and critical loads in a customer's facility. The algorithm and merits of this method are explained in detail. The detection characteristics are then analyzed using the ATP (Alternative Transients Program) and are confirmed using a real‐time digital simulator, and it is shown that the method is useful for detecting voltage sag. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 34–41, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20117     

An efficient algorithm for finding all DC solutions of piecewise‐linear circuits

An efficient algorithm is proposed for finding all DC solutions of transistor circuits where characteristics of transistors are represented by piecewise‐linear (PWL) convex monotone functions. This algorithm is based on a simple test (termed the linear programming, LP, test) for non‐existence of a solution to a system of PWL equations in a given region. In the conventional LP test, the system of PWL equations is transformed into an LP problem by surrounding component PWL functions by rectangles. Then the dual simplex method is applied, by which the number of pivotings per region becomes very small. In this letter, we propose a new LP test using the dual simplex method and triangles. The proposed test is not only efficient but also more powerful than the conventional test using the simplex method or rectangles. Copyright © 2008 John Wiley & Sons, Ltd.     

Higher‐order differentiation of network functions using signal flow graphs

This paper presents the application of signal flow graphs (SFG) in the calculation of higher‐order derivatives (sensitivities) of the linear circuit functions. The idea of exact differentiation of the circuit functions is based on the adjoint networks, translated into SFG language. Thanks to its application, it is possible to calculate the exact value of any order derivative of circuit function without knowing this function in explicit form. Moreover, these derivatives can be determined on the basis of analysis of only two graphs (circuits): the original and adjoint one. We show that the SFG approach to the sensitivity calculation allows to reduce greatly the complexity of calculations. Copyright © 2011 John Wiley & Sons, Ltd.     

Asymptotic stabilization and synchronization of parametric LCR resonant circuit using the characteristics of its coefficients

In this paper, we analyze stability of a time‐varying system represented by second‐order vector differential equations based on the characteristics of their coefficient matrices. New sufficient conditions for asymptotic stability of the equilibrium points are derived. Then, an asymptotic stabilizing control method of parametric LCR resonant system is discussed by using the obtained sufficient conditions. A method synchronizing two parametric LCR resonant systems is also given. The effectiveness of the results is illustrated by numerical examples. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(3): 48–55, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20142     

Improved analogue fault coverage estimation using probabilistic analysis

A method for fault detection probability estimation using statistical multi‐parameter circuit simulation is proposed, in order to check circuits for which double or multiple analogue measurements are utilized. Theoretical analysis for the estimation of the fault coverage is given, based on conditional probability calculations. The proposed method can be applied for both test measurement and input stimulus selection. Simulation results from the application of the method on typical analogue circuits—filter and amplifier—are given, showing a sufficient improvement over the fault coverage achieved by single measurements. Copyright © 2009 John Wiley & Sons, Ltd.     

Magnetic field analysis by the edge element FEM

Several useful techniques are presented for magnetic field analysis by the edge element FEM. The relations of nodal, edge, and facet shape functions are visualized as important properties using the differential operators of gradient and rotation. These shape functions and the rotation of edge shape functions are presented for tetrahedral, prismatic, pyramidal, and hexahedral elements. Furthermore, the method of determining coil current distributions satisfied with conservation of current is shown using a current vector potential and a surface tree gauge condition for open‐loop coils and closed loop coils. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(1): 59–65, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20168     

Development and experimental validation of automatic conversion procedure from mechanical to electrical connection for MEMS equivalent circuit

This paper describes equivalent circuit for micro electromechanical system (MEMS) using a type of behavior model for expressing mechanical and electromechanical element within circuit simulation, in order to simulate their dynamic behaviors easily. To fully treat the equivalent circuit as the behavior model, the equivalent interconnection expression for mechanical splice is required. In this work, a new approach has been proposed for converting the system composed of mechanical and electromechanical elements to equivalent circuit expression. This approach consists of substitution of unit equivalent elements and conversion of each equivalent interconnection for mechanical splices. We applied graph theory for equivalent interconnection. With this approach, complex MEMS consisting of a number of transducers and mechanical elements can be easily converted into equivalent circuits. In order to validate this approach, the resonant property of electrostatic comb-drive actuator was simulated using the equivalent circuit generated and measured experimentally. The simulated resonant frequency was in good agreement with the measurement and the admittance characteristics were well described using this circuit with a consideration of coupling capacitances at the comb electrodes. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Identification of system characteristics of a power system with time series data. Identification of frequency fluctuation characteristics of a small‐scale isolated system

Understanding actual characteristics of a power system with recorded time series data is of great importance, for example, in improving the performance of the system. Although system identification is a well‐known technique to achieve this goal, its applicability to a certain system should be examined for the particular case because its accuracy highly depends on the inherent characteristics of the system. While many papers have discussed application of a system identification technique to a power system, few papers have examined its applicability to the actual data of a power system. This paper presents a new system identification method to estimate characteristics of a power system while using output of intermittent generators or fluctuating loads as an external disturbance. The method employs cross spectra and coherence as a key factor in the identification; it estimates a transfer function of a power system, contribution of observed disturbance to total disturbance, and so on. The method is applied to time series data of two model systems: simulation results and measured data of an isolated power system with diesel generators. The study gives satisfactory results; implication on the accuracy of the method is discussed through the sample studies. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(3): 36–45, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20051     

Non‐linear circuit modelling via nodal methods

We discuss in this paper several interrelated nodal methods for setting up the equations of non‐linear, lumped electrical circuits. A rather exhaustive framework is presented, aimed at surveying different approaches and terminologies in a comprehensive manner. This framework includes charge‐oriented, conventional, and hybrid systems. Special attention is paid to so‐called augmented node analysis (ANA) models, which somehow articulate the tableau and modified node analysis (MNA) approaches to non‐linear circuit modelling. We use a differential–algebraic formalism and, extending previous results proved in the MNA context, we provide index‐1 conditions for augmented systems, which are shown to be transferred to tableau models. This approach gives, in particular, precise conditions for the feasibility of certain state‐space reductions. We work with very general assumptions on device characteristics; in particular, our approach comprises a wide range of resistive devices, going beyond voltage‐controlled ones. Copyright © 2005 John Wiley & Sons, Ltd.     

An efficient piecewise‐linear DC analysis method for general non‐linear circuits

The convergence problems of conventional DC analysis can be partly avoided by using piecewise‐linear analysis. This paper proposes a piecewise‐linear DC analysis method that can efficiently handle arbitrary couplings between non‐linear circuit elements. Piecewise‐linear modelling of the non‐linear circuit elements is automatically performed during simulation, using simplicial subdivisions. The number of linear regions, and thereby iterations, is considerably reduced by combining the common parts of separate simplicial subdivisions. Due to these reasons and since the method is formulated with the commonly used modified nodal approach, it has been possible to implement the method in the general‐purpose circuit simulator APLAC. The correct operation of the method is demonstrated with three examples. Copyright © 1999 John Wiley & Sons, Ltd.     

Evaluation of instantaneous power by the aspectum in the theory of the natural observation method

In this paper signal processing by aspectum was applied to actual waveforms for the first time. Aspectum is the quantity to estimate the instantaneous power on the theory of natural observation method, which was proposed by Iijima. It can quantitatively evaluate the instantaneous power of signals. To begin with, characteristics of the aspectum were clearly shown by applying it to known model signals. The result of analysis of observed electromagnetic field signals radiated by lightning discharge was shown as a sample applying aspectum to actual waveforms. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(1): 25–33, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20130     

Some invariant sums of higher‐order sensitivities

In this paper, a new class of invariant sensitivity sums of higher‐order sensitivities is given. Sensitivity sums considered are relevant to a network function of general lumped time‐invariant circuits containing passive and active elements. It is assumed that the circuit is linear and consists of one‐port elements and two‐port elements only. A part of the one‐port elements is described by admittance parameters and the other part by impedance parameters. The rest of the one‐port elements are independent sources. Two‐port elements are only controlled sources. Hybrid matrix should describe functional relationships of the elements. Formulas for invariant sums of sensitivities of first, second, third, and fourth order are presented. Copyright © 2008 John Wiley & Sons, Ltd.     

A three‐phase constant‐current source using an immittance converter

The term immittance converter refers to an impedance–admittance converter. The immittance converter has an input impedance that is proportional to the admittance of the load connected across output terminals. In this converter, the output current is proportional to the input voltage and the input current is proportional to the output voltage. Consequently, it converts a constant‐voltage source into a constant‐current source and a constant‐current source into a constant‐voltage source. It is well known that the quarter wavelength transmission line shows immittance conversion characteristics. However, it has a very long line length for the switching frequency, and is not suitable for power electronics applications. We thus proposed immittance converters that consist of lumped elements L, C and show improved immittance conversion characteristics at a resonant frequency. A three‐phase constant‐current source is proposed in this paper. It is possible to realize this by a simple circuit using an immittance converter. In this paper, circuit operation, characteristic equations, and results of simulation are described. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(4): 47–54, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20078