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1 – 3 of 3Stéphane 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 sheet stack…
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
Keywords
Mohamed Omar Younsi, Olivier Ninet, Fabrice Morganti, Jean-Philippe Lecointe, Farid Zidat and Matthieu Buire
This paper aims to study the influence of supply voltage variations on the external magnetic field emitted by grid-powered induction machines (IMs).
Abstract
Purpose
This paper aims to study the influence of supply voltage variations on the external magnetic field emitted by grid-powered induction machines (IMs).
Design/methodology/approach
Two models are developed in the paper to analyse, for different supply voltage values, the influence of the variations of the magnetizing voltage for which there is a link with the tangential component of the external flux. The first is an analytical model based on the IM single-phase-equivalent circuit with variable magnetizing reactance to take into account the saturation of the magnetic circuit. The second is a numerical finite element simulation to model the same phenomenon. Results of both models are analysed with experimental measures of the external flux.
Findings
The study shows that the amplitude of the external field strongly depends on supply voltage values.
Research limitations/implications
The investigation is mainly focused on the tangential component of the external magnetic field which is of high importance concerning the applicability of non-invasive methods of diagnosis, as electromagnetic torque estimation developed by the authors or internal fault determination.
Originality/value
The originality of the paper concerns the characterization of the external flux with the supply voltage for IMs. It is shown that the magnetic circuit radiates external flux differently with the load and with the supply voltage.
Details
Keywords
Youcef Zeroukhi, Ewa Napieralska Juszczak, Krzysztof Komeza, Fabrice Morganti and Guillaume Vega
In the majority of devices for measuring the resistance of wires or cables, the supplying voltage is applied via some clamping arrangement. Thus, current enters the bundle of…
Abstract
Purpose
In the majority of devices for measuring the resistance of wires or cables, the supplying voltage is applied via some clamping arrangement. Thus, current enters the bundle of conductors through the side surface of the outside wire. The purpose of this project was to establish the distance from the supplying point after which the current may be considered to be uniform and normal to the cable cross‐section.
Design/methodology/approach
When current passes from one wire to another, the crucial parameter is the resistance of the contact region. The paper presents a method by which this region can be identified and relevant resistance measured. A comprehensive simulation was conducted for different types of wires and cables to assess the influence of design parameters on the current distribution and uniformity.
Findings
The distance from the current entry point (the clamps) to the position where current density may be considered uniform has been established. This has facilitated estimating recommended positions of voltage taps with reference to current taps.
Practical implications
The look‐up tables and graphs allow adjustments to the position of the taps and/or correction of the measured results.
Originality/value
The original contribution of this paper is in the way the contact region is identified where current passes from one wire to another. Original relationships have been proposed showing the relationship between contact resistance and the design parameters of the cable and mechanical stress.
Details