1. Department of Electrical Machines, Drives and Measurements, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland
2. SAFRAN Electrical & Power, Parc d’activité d’Andromède, 1, rue Louis Blériot, 31702 Blagnac Cedex, France
3. Department of Pure Mathematics, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland
4. Department of Mining, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland