1. Institute of Electrical Machines (IEM); RWTH Aachen University; Schinkelstr. 4 D-52056 Aachen Germany
2. IMMc; Université Catholique de Louvain; Av. G. Lemaitre B-1348 Louvain-la-Neuve Belgium
3. Department of Electrical Engineering and Computer Science; Université de Liège; Grande Traverse 10 B-4000 Liège Belgium