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Article
Publication date: 27 March 2020

Stéphane Duchesne, Fabrice Morganti, Carl Shulz and Daniel Roger

This study presents a new method for the detection of faults in large transformer cores. It is based on the analysis of leakage flux components in the vicinity of the…

Abstract

Purpose

This study presents a new method for the detection of faults in large transformer cores. It is based on the analysis of leakage flux components in the vicinity of the sheet stack. The purpose of this study is to provide a nondestructive analysis tool for transformer cores during the assembly process to detect accidental defects such as inter-laminar short circuits.

Design/methodology/approach

The different components of the leakage flux allow localization of the fault in the stack and also permit to assess its severity. Out of the many kinds of defects which may appear in a transformer core, this method only detects those which actually cause an increase in the transformer’s global iron losses, which are thus the most detrimental.

Findings

The proposed method allows a more efficient control of the quality of the cores during their manufacturing process. Until now, it was only possible to know the quality of the core when the transformer was fully assembled.

Research limitations/implications

The accuracy of the method depends on the size of the defect and may request many measurements to give usable information.

Practical implications

Controlling iron losses in a core during its construction avoids heavy dismantling operations, both financially and temporally.

Originality/value

This method can help transformer manufacturers optimize their building process. In addition, the method remains effective regardless of the size of the core considered.

Details

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

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Article
Publication date: 20 September 2018

Daniel Roger and Ewa Napieralska-Juszczak

High-temperature (HT°) motors are made with inorganic coils wound with a ceramic-coated wire. They must be carefully designed because the HT° insulating materials have a…

Abstract

Purpose

High-temperature (HT°) motors are made with inorganic coils wound with a ceramic-coated wire. They must be carefully designed because the HT° insulating materials have a lower breakdown voltages than the polymers used for insulating standard machines.

Design/methodology/approach

The voltage distribution between stator coils is computed with high-frequency (HF) equivalent circuits that consider the magnetic couplings and the stray capacitances. Two time scales are used for getting a fast computation of very short voltage spikes. For the first step, a medium time scale analysis is performed considering a simplified equivalent circuit made without any stray capacitance but with the full PWM pattern and the magnetic couplings. For the second step, a more detailed HF equivalent circuit computes voltage spikes during short critical time windows.

Findings

The computation made during the first step provides the critical time windows and the initial values of the state variables to the second one. The rise and fall time of the electronic switches have a minor influence on the maximum voltage stress. Conversely, the connection cable length and the common-mode capacitances have a large influence.

Research limitations/implications

HF equivalent circuits cannot be used with random windings but only to formed coils that have a deterministic position of turns.

Practical implications

The proposed method can be used designing of HT° machine windings fed by PWM inverter and for improving the coils of standard machine used in aircraft’s low-pressure environments.

Originality/value

The influence of grounding system of the DC link is considered for computing the voltage spikes in the motor windings.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 5
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 7 November 2016

Daniel Roger, Vadim Iosf and Sylvain Babicz

The purpose of this paper is to present a method for computing voltage spikes endured by the insulation of the first coils of high-temperature (HT°) synchronous machines…

Abstract

Purpose

The purpose of this paper is to present a method for computing voltage spikes endured by the insulation of the first coils of high-temperature (HT°) synchronous machines fed by PWM inverters that deliver fast-fronted voltage pulses.

Design/methodology/approach

The transient state following each steep edge is computed by SPICE using the global high-frequency (HF) equivalent circuit of the motor winding. This equivalent circuit is automatically built using the proposed elementary coil model. Two inorganic HT° technologies are compared: the first one uses a round copper wire insulated by a thin ceramic layer and the second one is made with an anodized aluminum strip.

Findings

The winding made with an anodized aluminum strip, which has a higher turn-to-turn capacitance, yields a better voltage distribution between coils of the machine.

Research limitations/implications

The elementary coil equivalent circuit is computed from impedance measurements performed on an elementary coil. Another starting point could be developed with an FE analysis to determine the parameters of the HF equivalent circuit, which would avoid the need for a prototype coil before the machine design.

Practical implications

For inorganic motors, the insulation layers have poorer electrical characteristics compared with standard organic ones. Therefore, the computation of voltage spikes distribution along the coils of each phase represents a major issue in the design of HT° machines.

Originality/value

The presented approach is a step toward the design of HT° (400-500°C) actuators fed by PWM inverters based on fast SiC electronic switches.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 35 no. 6
Type: Research Article
ISSN: 0332-1649

Keywords

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Article
Publication date: 18 January 2019

Marcin Lefik, Krzysztof Komeza, Ewa Napieralska-Juszczak, Daniel Roger and Piotr Andrzej Napieralski

The purpose of this paper is to present a comparison between reluctance synchronous machine-enabling work at high internal temperature (HT° machine) with laminated and solid rotor.

Abstract

Purpose

The purpose of this paper is to present a comparison between reluctance synchronous machine-enabling work at high internal temperature (HT° machine) with laminated and solid rotor.

Design/methodology/approach

To obtain heat sources for the thermal model, calculations of the electromagnetic field were made using the Opera 3D program including effect of rotation and the resulting eddy current losses. To analyse the thermal phenomenon, the 3D coupled thermal-fluid (CFD) model is used.

Findings

The presented results show clearly that laminated construction is much better from a point of view of efficiency and temperature. However, solid construction can be interesting for high speed machines due to their mechanical robustness.

Research limitations/implications

The main problem, despite the use of parallel calculations, is the long calculation time.

Practical implications

The obtained simulation and experimental results show the possibility of building a machine operating at a much higher ambient temperature than it was previously produced for example in the vicinity of the aircraft turbines.

Originality/value

The paper presents the application of fully three-dimensional coupled electromagnetic and thermal analysis of new machine constructions designed for elevated temperature.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 38 no. 4
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 14 August 2007

Stéphane Duchesne, Ewa Napieralska‐Juszczak and Daniel Roger

A new model able to describe the high frequency (HF) behaviour of the laminated cores of AC machines is proposed. The aim is to compute the external flux density of…

Abstract

Purpose

A new model able to describe the high frequency (HF) behaviour of the laminated cores of AC machines is proposed. The aim is to compute the external flux density of machine cores, corresponding to electromagnetic emissions in the HF range when the skin effect is predominant.

Design/methodology/approach

For high frequencies, the skin depth is much lower than the thickness of a lamination and the external flux density is determined using a new analytical model. The validity of this model is confirmed by measurements performed on a magnetic core representing a small part of a large machine and a finite element 3D simulation.

Findings

For high frequencies, the external flux density is computed considering an equivalent current layer flowing on the laminated core external surface. Eddy currents in the laminated core have a large influence on the current density in this current layer.

Research limitations/implications

The new model proposed is valid when the skin depth is lower than half the thickness of a lamination.

Practical implications

The knowledge of the machine magnetic core behaviour in the frame of the HF electromagnetic emissions has practical applications for large AC machine maintenance such as the localization of partial discharges in the winding insulation. With this model, it is possible to analyse the information given by small magnetic sensors placed between the machine core and the external frame to solve all the insulation problems.

Originality/value

The new proposed model is able to establish a link between the electric HF phenomena in the windings of a working machine and the magnetic flux density outside the laminated core.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 26 no. 4
Type: Research Article
ISSN: 0332-1649

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Book part
Publication date: 29 May 2009

Daniel J. Phaneuf and Roger H. von Haefen

In this chapter, we describe how random utility maximization (RUM) discrete choice models are used to estimate the demand for commodity attributes in…

Abstract

In this chapter, we describe how random utility maximization (RUM) discrete choice models are used to estimate the demand for commodity attributes in quality-differentiated goods. After presenting a conceptual overview, we focus specifically on the conditional logit model. We examine technical issues related to specification, interpretation, estimation, and policy use. We also discuss identification strategies for estimating the role of price and non-price attributes in preferences when product attributes are incompletely observed. We illustrate these concepts via a stylized application to new car purchases, in which our objective is to measure preferences for fuel economy.

Details

Quantifying Consumer Preferences
Type: Book
ISBN: 978-1-84855-313-2

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Article
Publication date: 11 May 2010

Drago Dolinar, Petar Ljušev, Gorazd Štumberger, Matjaž Dolinar and Daniel Roger

The purpose of this paper is to analyze the impact of magnetic saturation on the steady‐state operation of the induction motor (IM) drive in regard to rotor field‐oriented…

Abstract

Purpose

The purpose of this paper is to analyze the impact of magnetic saturation on the steady‐state operation of the induction motor (IM) drive in regard to rotor field‐oriented control (RFOC). The aim of the presented two methods is to obtain the required steady‐state torque with minimal stator current, which thus reduces stator coper losses considerably.

Design/methodology/approach

The first method is based on an analytic calculation of the peak torque‐per‐ampere ratio curve of saturated IM. The torque characteristics obtained at a constant stator current are used to calculate that value of magnetizing current which gives the minimal stator current for the required load torque. The second method directly searches the minimal stator current for the required load torque. Experiments completely confirm the efficiency of the proposed selection of a magnetizing current reference.

Findings

Operation of the IM drive strongly depends on a proper selection of the rotor flux linkage reference value, the selection of which represents an additional degree of freedom in control design. Therefore, it can be used to optimize some of those drive features subjected to voltage and current constraints. The proposed calculation procedure is simple so that can be easily implemented in practically application. However, some additional IM data like magnetizing curve, inertia moment, and coefficient of viscous friction are necessary.

Originality/value

The substantial impact of saturation on the stead‐state torque characteristics of IM, determined for the constant stator current and the constant d‐axis stator current, is determined analytically and numerically.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 29 no. 3
Type: Research Article
ISSN: 0332-1649

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Book part
Publication date: 11 June 2001

Abstract

Details

Social Capital of Organizations
Type: Book
ISBN: 978-0-76230-770-8

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Book part
Publication date: 15 July 2009

Stewart R. Miller, Roger Calantone, Daniel C. Indro and Malika Richards

Many studies of control and international joint venture (IJV) performance have focused on ownership and management control. We develop a conceptual framework to explain…

Abstract

Many studies of control and international joint venture (IJV) performance have focused on ownership and management control. We develop a conceptual framework to explain how strategies affect the relationship between management control and joint venture performance. Specifically, we focus on serving the host-country customer and extending the life cycle of the foreign partner's products. Using a sample of Sino–U.S. and Sino–Japanese joint ventures, we found that serving the host-country customer strengthens the positive relationship between management control by the foreign partner and IJV performance. However, extending the product life cycle of the foreign partner's products weakens the positive relationship between management control by the foreign partner and IJV performance. We discuss the performance implications of dealing with both strategies and reveal a complex relationship between equity ownership, management control, and IJV performance.

Details

Managing, Subsidiary Dynamics: Headquarters Role, Capability Development, and China Strategy
Type: Book
ISBN: 978-1-84855-667-6

Content available
Article
Publication date: 29 November 2011

Henry A. Davis

Abstract

Details

Journal of Investment Compliance, vol. 12 no. 4
Type: Research Article
ISSN: 1528-5812

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