A.T. Klyuchnikov - Ph.D. (Eng.), Associate Professor, Department «Electrical Engineering and Electromechanics», Perm National Research Polytechnic University. E-mail: aklu2011@pstu.ru A.D. Korotaev - Ph.D. (Eng.), Associate Professor, Department of «Electrical Engineering and Electromechanics», Perm National Research Polytechnic University. E-mail: lis@pstu.ru D.A. Chirkov - Assistant, Department «Electrical Engineering and Electromechanics», Perm National Research Polytechnic University. E-mail: chirkov146@mail.ru