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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.

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.

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.

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

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

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

The purpose of this paper is to exploit the optimal performances of each magnetic material in terms of low iron losses and high saturation flux density to improve the efficiency and the power density of the selected motor.

This paper presents a study to improve the power density and efficiency of e-motors for electric traction applications with high operating speed. The studied machine is a yokeless-stator axial flux permanent magnet synchronous motor with a dual rotor. The methodology consists in using different magnetic materials for an optimal design of the stator and rotor magnetic circuits to improve the motor performance. The candidate magnetic materials, adapted to the constraints of e-mobility, are made of thin laminations of Si-Fe nonoriented grain electrical steel, Si-Fe grain-oriented electrical steel (GOES) and iron-cobalt Permendur electrical steel (Co-Fe).

The mixed GOES-Co-Fe structure allows to reach 10 kW/kg in rated power density and a high efficiency in city driving conditions. This structure allows to make the powertrain less energy consuming in the battery electric vehicles and to reduce CO₂ emissions in hybrid electric vehicles.

The originality of this study lies in the improvement of both power density and efficiency of the electric motor in automotive application by using different magnetic materials through a multiobjective optimization.

This paper aims to model a three-dimensional twisted geometry of a twisted pair studied in an electrostatic approximation using only two-dimensional (2D) finite elements.

The proposed method is based on the reformulation of the weak formulation of the electrostatics problem to deal with twisted geometries only in 2D.

The method is based on a change of coordinates and enables a faster computational time as well as a high accuracy.

The effectiveness of the adopted approach is demonstrated by studying different configurations related to the IEC 60851-5 standard defined for the measurement of the electrical properties of the insulation of the winding wires used in electrical machines.

This paper aims to propose a high‐frequency (HF) model able to compute the flux density in the vicinity of the laminated stator core of an AC machine.

Experiments form the main approach. Analytical results previously obtained with a simplified rectangular laminated structure are confirmed with a standard cylindrical magnetic core.

Three frequency domains are defined, depending on the skin depth relative to the thickness of the magnetic sheets. A methodological approach is proposed for each domain. For higher frequencies, the magnetic core can be considered as transparent for external field computation.

The HF model is valid for skin depths much lower than the thickness of the magnetic sheets.

The proposed HF model provides a link between the weak field measured in the natural void existing between the stator core and the housing of large electrical machines. With such a link, it is possible to develop a new monitoring system able to detect and to localize the partial discharges in the stator winding of a large machine.

The low‐frequency limit of the model has been measured. It corresponds to a ratio of 1/40 between the skin depth and the magnetic sheet thickness. Therefore this model offers a new perspective for maintenance applications.

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.

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.

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.

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

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.

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.

Restrictions on social interaction and travel due to the COVID-19 pandemic have affected how researchers approach fieldwork and data collection. Whilst online focus groups have received attention since the 2000s as a method for qualitative data collection, relatively little of the relevant literature appears to have made use of now ubiquitous video calling software and synchronous, interactive discussion tools. Our own experiences in organising fieldwork aimed at understanding the impact of different “future-proofing” strategies for the European agri-food system during this period resulted in several methodological changes being made at short notice. We present an approach to converting in-person focus group to a virtual methodology and provide a checklist for researchers planning their own online focus groups. Our findings suggest data are comparable to in-person focus groups and factors influencing data quality during online focus groups can be safeguarded. There are several key steps, both before and during the focus groups, which can be taken to ensure the smooth running of such events. We share our reflections on this approach and provide a resource for other researchers moving to online-only data collection.