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Article
Publication date: 1 February 1966

T. PALMER

It is fairly well known that nowadays Ohm's law has two meanings:

Abstract

It is fairly well known that nowadays Ohm's law has two meanings:

Details

Education + Training, vol. 8 no. 2
Type: Research Article
ISSN: 0040-0912

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Article
Publication date: 10 April 2019

Mohammad Amin Jarrahi, Emad Roshandel, Mehdi Allahbakhshi and Mohammad Ahmadi

This paper aims to achieve an optimal design for distribution transformers considering cost and power losses. Particle swarm optimization (PSO) algorithm is used as an…

Abstract

Purpose

This paper aims to achieve an optimal design for distribution transformers considering cost and power losses. Particle swarm optimization (PSO) algorithm is used as an optimization tool for minimizing the objective functions of design procedure which are cost and electrical and iron losses.

Design/methodology/approach

In this paper, distribution transformer losses are considered as operating costs. Also, transformer construction cost which depends on the amount of iron and copper in the structure is assumed as its initial cost. In addition, some other important constraints such as appropriate ranges of transformer efficiency, voltage regulation, temperature rise, no-load current, and winding fill factor are investigated in the design procedure. The PSO algorithm is applied to find optimum amount of needed copper and iron for a typical distribution transformer. Moreover, transformer impedance considered as a constraint to achieve an acceptable voltage regulation in the design process.

Findings

It is shown that the proposed design procedure provides a simple and effective approach to estimate the flux and current densities for minimizing the active part cost and active power losses which means reduction in amount of transformer total owning cost (TOC).

Originality/value

The methodology advances a proposal for reducing distribution transformers costs using PSO algorithm. The approach considers the aforementioned constraints and TOC to minimize the active part cost and maximize the efficiency. It is demonstrated that a designed transformer will not be optimum when the transformer losses over years are not considered in design procedure. Finally, the results prove the effectiveness of the proposed procedure in designing cost-effective distribution transformers from its initial cost until its whole life.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 38 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 6 November 2017

Siva Reddy Sheri, Chamkha Ali. J. and Anjan Kumar Suram

The purpose of this paper is to analyze the thermal-diffusion and diffusion-thermo effects on magnetohydrodynamics (MHD) natural convective flow through porous medium in a…

Abstract

Purpose

The purpose of this paper is to analyze the thermal-diffusion and diffusion-thermo effects on magnetohydrodynamics (MHD) natural convective flow through porous medium in a rotating system with ramped temperature.

Design/methodology/approach

Using the non-dimensional variables, the flow governing equations along with corresponding initial and boundary conditions have been transformed into non-dimensional form. These non-dimensional partial differential equations are solved by using finite element method. This method is powerful and stable. It provides excellent convergence and flexibility in providing solutions.

Findings

The effects of Soret number, Dufour number, rotation parameter, magnetic parameter, Hall current parameter, permeability parameter, thermal Grashof number, solutal Grashof number, Prandtl number, thermal radiation parameter, heat absorption parameter, Schmidt number, chemical reaction parameter and time on the fluid velocities, temperature and concentration are represented graphically in a significant way and the influence of pertinent flow governing parameters on the skin frictions and Nusselt number are presented in tabular form. On the other hand, a comparison for validation of the numerical code with previously published work is performed, and an excellent agreement is observed for the limited case existing literature.

Practical implications

A very useful source of information for researchers on the subject of MHD flow through porous medium in a rotating system with ramped temperature.

Originality/value

The problem is moderately original, as it contains many effects like thermal-diffusion (Soret) and diffusion-thermo (Dufour) effects and chemical reaction.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 11
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 21 October 2019

Cem Civelek

The purpose of this study is the application of the following concepts to the time discrete form. Variational Calculus, potential and kinetic energies, velocity…

Abstract

Purpose

The purpose of this study is the application of the following concepts to the time discrete form. Variational Calculus, potential and kinetic energies, velocity proportional Rayleigh dissipation function, the Lagrange and Hamilton formalisms, extended Hamiltonians and Poisson brackets are all defined and applied for time-continuous physical processes. Such processes are not always time-continuously observable; they are also sometimes time-discrete.

Design/methodology/approach

The classical approach is developed with the benefit of giving only a short table on charge and flux formulation, as they are similar to the classical case just like all other formulation types. Moreover, an electromechanical example is represented as well.

Findings

Lagrange and Hamilton formalisms together with the velocity proportional (Rayleigh) dissipation function can also be used in the discrete time case, and as a result, dissipative equations of generalized motion and dissipative canonical equations in the discrete time case are obtained. The discrete formalisms are optimal approaches especially to analyze a coupled physical system which cannot be observed continuously. In addition, the method makes it unnecessary to convert the quantities to the other. The numerical solutions of equations of dissipative generalized motion of an electromechanical (coupled) system in continuous and discrete time cases are presented.

Originality/value

The formalisms and the velocity proportional (Rayleigh) dissipation function aforementioned are used and applied to a coupled physical system in time-discrete case for the first time to the best of the author’s knowledge, and systems of difference equations are obtained depending on formulation type.

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Article
Publication date: 6 June 2016

Bo Hu, Runqiao Yu and Jian Liu

This paper aims to clarify the transient electromagnetic method used for the nondestructive testing of the corrosion of an in-service buried metal pipeline in trenchless state.

Abstract

Purpose

This paper aims to clarify the transient electromagnetic method used for the nondestructive testing of the corrosion of an in-service buried metal pipeline in trenchless state.

Design/methodology/approach

The paper designed corrosion models indoor and infield for testing. A method for calculating the residual wall thickness of metal pipelines was also proposed. The calculation method was verified by the test results. In the test, the receiving probe was improved by the addition of a Mn-Zn ferrite core. The amplitudes of the test results obviously increased, and the calculation accuracy was improved.

Findings

The paper states that the transient electromagnetic method can detect the uniform corrosion distribution of a certain section of a pipeline. A multi-channel profile of the induced electromotive force and the calculated values of the residual wall thickness can be used to confirm the position and degree of corrosion defects, respectively.

Research limitations/implications

The transient electromagnetic method is more effective for large-area corrosion than for localized corrosion (pitting).

Practical implications

The paper includes implications for the development of nondestructive testing method of the corrosion of an in-service buried metal pipeline.

Originality/value

This paper proved the feasibility and reliability of using transient electromagnetic method to test the corrosion of a buried metal pipeline based on experimental study.

Details

Anti-Corrosion Methods and Materials, vol. 63 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

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Article
Publication date: 1 February 1993

J.V. Manca, L. De Schepper, W. De Ceuninck, M. D'Olieslager, L.M. Stals, M.F. Barker, C.R. Pickering, W.A. Craig, E. Beyne and J. Roggen

In this paper, it is shown that the so‐called in‐situ electrical measurement technique is a valuable tool for understanding failure mechanisms in thick film dielectrics…

Abstract

In this paper, it is shown that the so‐called in‐situ electrical measurement technique is a valuable tool for understanding failure mechanisms in thick film dielectrics. The technique makes it possible to measure important electrical characteristics of thick film dielectric systems in the temperature range from room temperature up to 900°C. This information is essential to understand failure mechanisms and to optimise the system with respect to quality and reliability. Mainly two electrical properties have been investigated: (i) the electrical resistance of the dielectric as a function of temperature and (ii) the spontaneous electromotive force occurring at higher temperatures between two metal layers with the dielectric in between. A significant result of the work is the observation of a close correlation between the leakage current measured through the dielectric at elevated temperatures, and the ability of the dielectric to resist shorting and blistering effects during the preparation of circuits. Secondly, from in‐situ voltage measurements, it was confirmed that the mixed metallurgy system Au(bottom)‐dielectric‐Ag(top) acts at 850°C as a spontaneous battery, and the battery voltage (i.e., the spontaneous electromotive force) was measured. Depending on the type of dielectric, a battery voltage up to 200 mV between the two metal layers was observed. As a result of this spontaneous electromotive force, blistering occurs. The battery voltage was shown to be much smaller in unmixed metallurgy systems with Ag(bottom)‐dielectric‐Ag(top) or Au(bottom)‐dielectric‐Au(top). However, if an external voltage of 300 mV is applied to such a system during a temperature profile up to 850°C, blisters can also be induced. This shows unambiguously that blistering is a voltage driven effect.

Details

Microelectronics International, vol. 10 no. 2
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 1 December 2004

Andrzej Demenko, Lech Nowak and Wojciech Pietrowski

This paper presents the finite element method for the calculation of open‐circuit characteristic of a squirrel cage machine with saturated core. The flux linkage with the…

Abstract

This paper presents the finite element method for the calculation of open‐circuit characteristic of a squirrel cage machine with saturated core. The flux linkage with the stator winding and the winding inductances have been calculated using the edge element method. The calculations show that the equivalent inductance of a balanced three‐phase no‐loaded induction machine with saturated core may be defined like a quadrature‐axis inductance in synchronous machine. The algorithm of this inductance calculation has been proposed. The equivalent inductances have been used in the calculation of electromotive force. The results obtained from numerical calculations have been compared with the measured results.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 23 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 7 September 2012

Rafal M. Wojciechowski, Cezary Jedryczka, Piotr Lukaszewicz and Dariusz Kapelski

The purpose of this paper is to investigate application possibilities of soft magnetic composites (SMC) in the design of high speed permanent motors for home appliances.

Abstract

Purpose

The purpose of this paper is to investigate application possibilities of soft magnetic composites (SMC) in the design of high speed permanent motors for home appliances.

Design/methodology/approach

The design of high speed permanent magnet motor (HSPM) with core made of SMC has been proposed. The governing information about SMC has been presented. The possible advantages and disadvantages of applying magnetic powder materials in the design of electrical machines have been studied. To solve the partial differential equations describing magnetic vector distribution in considered HSPM, the edge element method (EEM) has been applied. The formulas of permanent magnet and winding descriptions, and electromagnetic torque calculations have been presented and studied. To verify accuracy of methodology and functionality of the elaborated software, a prototype of the considered motor has been built and the experimental setup for testing torque and electromotive force has been elaborated. The comparison between measured and simulated motor characteristics have been presented and discussed.

Findings

Comparison between measured and simulated motor characteristics proves the model accuracy. The obtained results show that the designed HSPM motor has sinusoidal electromotive force waveforms, low cogging torque value and the sinusoidal torque versus rotor angle characteristics. Moreover, it has been indicated that the application of SMC materials can reduce power losses in the high speed motors.

Originality/value

The paper describes the development of the numerical method and software for analysis of HSPM with core made of powder materials.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 31 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 10 May 2011

Thomas S. Parel, Mihai D. Rotaru, Jan K. Sykulski and Grant E. Hearn

The purpose of this paper is to optimise the cost‐based performance of a tubular linear generator and to minimise cogging forces.

Abstract

Purpose

The purpose of this paper is to optimise the cost‐based performance of a tubular linear generator and to minimise cogging forces.

Design/methodology/approach

Optimisation of a tubular linear generator with longitudinal flux topology has been undertaken using a finite element method. The computational models used have been verified experimentally.

Findings

The use of an oversized stator linear generator design as opposed to an oversized translator design has the potential to increase the output electromotive force per unit material cost by 25 per cent for slotless iron core topologies and approximately 14 per cent for air core topologies. For cogging force minimisation, optimisation of the length of the stator core is an effective technique for both oversized stator and oversized translator constructions. Comparisons of magnet materials also indicate that the higher cost of rare earth magnets to ferrites is compensated by their superior specific performances.

Originality/value

In this paper, a broader range of design parameters than in previous investigations has been optimised for the slotless iron core and air core topologies. The result relating to cogging force reduction and cost savings (in particular) has the potential to make direct drive wave energy extraction a more competitive technology in terms of reliability and cost.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 30 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 16 March 2010

Xiaoya He and Yi Lin

The purpose of this paper is to investigate yoyo potential difference and induction of electric yoyo flows by using the general systemic yoyo model and available…

Abstract

Purpose

The purpose of this paper is to investigate yoyo potential difference and induction of electric yoyo flows by using the general systemic yoyo model and available quantitative tools.

Design/methodology/approach

Empirical laws and well‐known laboratory experiments of physics are revisited in light of the spinning yoyo method and thinking logic. When appropriate, relevant quantitative methods are established.

Findings

By generalizing the concept of electromotive force, the paper introduces that of meridian motive forces (MMF). By considering two possible cases when electric yoyo flows can be induced within a return circuit, the paper uses specific examples to compute yoyo potential differences, the forces needed to pull a conductive wire in a magnetic yoyo field, and the total flux of magnetic yoyo field passing through a return circuit. When the paper tries to address the questions of how an electric yoyo current in a circuit is produced and what force could get around the resistance of metals to make electric yoyo charges move around inside return circuits, the paper successfully establishes a theoretical explanation for why Lenz's law about the direction of induced electric currents holds true. At the end, the paper develops a quantitative formula for practically calculating desired MMF.

Originality/value

This paper provides the first ever theoretical explanation for why Lenz's law could be true. It is expected that this explanation would be equally applicable in the study of social systems.

Details

Kybernetes, vol. 39 no. 2
Type: Research Article
ISSN: 0368-492X

Keywords

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