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Alexandre Giraud has defended his thesis on Electrical Engineering

On wednesday, December 13th 2017, Alexandre Giraud has defended his thesis. Awarded by INP Toulouse, his work was supervised by both LAPLACE laboratory (CNRS/INP-ENSEEIHT/UPS), the GEET doctoral school and IRT Saint Exupéry.

The high quality and the relevance of Alexandre’s thesis contributed to get significant results as a part of INTEGRATION project.

Thesis Subject

« Characterisation of magnetic materials and losses computation in stator Yoke of electrical machine operating at high frequency »

About this thesis

The work proposed here took place in IRT Saint-Exupéry in collaboration with Laplace Laboratory. It is part of a project aiming for the integration of electrical systems improvement in order to electrify aircraft. The development of electrical energy aboard aircraft has many advantages: mass gain, optimization facilitated… More precisely, the using of electrical machines is studied here. Actuator, compressor, a lot of system using non-electric energies can be changed for electrical machines. As in any energy conversion system, losses cannot be avoided and especially iron losses, which are the main topic of this thesis.

The airplane electrical networks, as well as electrical machine control devices, induce a large increase in iron loss proportion compared to other losses. Yields are diminishing but iron loss prediction is the main issue: electrical machines are oversized for safety, become less efficient and the mass gain is reduced. That is why the understanding of the behavior, or characterization, of magnetic materials used in electrical machines under non-ideal conditions is essential. On the other hand, it is necessary to improve the iron loss models in order to make their prediction efficient and to optimize the electrical machine modeling. The more precise their prediction, the more the factors influencing the losses will be determined. It will then be possible to envisage a more global optimization of the electromechanical chain. This thesis is a first step towards this global integration.

The magnetic material characterization was done under various conditions. First, one-dimensional flux density B have been studied. The influence of their spectrum on iron losses was the major purpose of this characterization: amplitude or frequency influence in the case of sinusoidal fields and then harmonic frequency or harmonic phase influence for more complex spectrum. Iron losses are very sensitive to these parameters.

Then, the proposed loss modelling goes through a reconstruction of the hysteresis cycle.  Therefore, it consists in predicting B from the H field. Based on Play model, this scalar quasi-static modelling has shown its accuracy and predictability. However, being scalar and quasi-static prevent the model from any time-dependence. An analytical model of eddy currents and a dynamization proposal has been developed. With an eddy current model, frequency effects would be taken into account and thus would complete the quasi-static model.


  • M. Yvan LEFEVRE – Laplace Laboratory – INP Toulouse – PhD Advisor
  • M. Jean-François LLIBRE – University of Toulouse Jean Jaurès – Co-Supervisor
  • M. Alix BERNOT – IRT Saint Exupère – Co-Supervisor
  • Mme. Afef LEBOUC – G2ELac – Grenoble INP – Rapporteur
  • M. Daniel MATT – IES – University of Montpellier II – Rapporteur
  • M. Nelson SADOWSKI – Federal University of Santa Catarina – Examiner
  • M. Laurent ALBERT – IRT Saint Exupéry – Invited


Optimizing the electro-mechanical chain, from converter to cable and motor.

Related Publications & Conference Communications

A. Giraud, A. Bernot, J-F. Llibre, Y. Lefèvre : “Influence du spectre de l’induction magnétique sur les pertes fer dans les stators de machines électriques”Symposium de Genie Electrique, Jun 2016, Grenoble, France

A. Giraud, A. Bernot, Y. Lefevre, J-F Llibre. : “Measurement of magnetic hysteresis swelling-up with frequency: impact on iron losses in electric machine sheets”. CMSM 2017 (International Workshop of Electronics, Control, Measurement, Signals and their application to Mechatronics), May 2017, Donostia, Spain. 2017 IEEE International Workshop of Electronics, Control, Measurement, Signals and their Application to Mechatronics (ECMSM), pp. 1-6, 2017

A. Bernot, A. Giraud, Y. Lefèvre, J-F. Llibre : “Experimental Study of Iron Losses Generated by a Uniform Rotating Field”. IEEE Transactions on Magnetics, Institute of Electrical and Electronics Engineers, 2017, 53 (11), pp.6300705.