1. Bombardier Transportation, 704-350 Wellington Str., Kingston, Ontario, K7K 7J7, Canada. E-mail: kworonow@transport.bombardier.com
2. Institute of Electrical Machines, Traction and Drives, Technical University Braunschweig, Hans-Sommer-Str. 66, 38106 Braunschweig, Germany. E-mail: r.palka@tu-bs.de