Erkki Lantto

Induction and permanent-magnet synchronous machines for high-speed applications

Solid-rotor induction motors are mechanically very robust and therefore potential candidates for highspeed electric drives. Permanent magnet machines offer better electromagnetic characteristics. These two types of machine are compared for high-speed applications. Electromagnetic, thermal and mechanical aspects are discussed. The permanent magnet machines are considered to be the best solution for applications in which the surface speed of the rotor remains below 250 m/s. For very large speeds and powers, a solid-rotor induction motor is preferred

Numerical Identification of Electromagnetic Force Parameters for Linearized Rotordynamic Model of Cage Induction Motors

The electromechanical interaction in cage induction motors induces additional forces between the rotor and stator. Recently, a linear parametric model was presented for these forces, and the corresponding model was combined with a mechanical rotor model. The electromagnetic system is usually non-linear due to the saturation of magnetic materials. Thus, the effective identification of the force parameters is crucial. Initially, the parameters were identified numerically from the response induced by the whirling rotor. Later on, a method based on the impulse response analysis was presented. The aim of this study was to present the theoretical background of this impulse method, and to present some useful additional features. The derived equations show the mathematical equivalency of this impulse method and the previous whirling method. The results show that the impulse method is numerically effective. In addition, the feasibility of thus obtained simple electromechanical rotor model was demonstrated.Copyright