Electromechanical modelling and active control of flexural rotor vibration in cage rotor electrical machines

The main objective of this thesis is to develop new tools for model-based control of flexural rotor vibration in cage induction machines. In order to exert the control force on the rotor, a built-in force actuator based on self-bearing principle is considered. A low-order parametric electromechanical model coupling the eccentric-rotor machine, the actuator and rotor-dynamics is developed. Furthermore, numerical analysis of the actuator-rotor system is considered. The numerical analysis is based on time-discretised finite element analysis of the electromagnetic fields in the two-dimensional cross-section of the machine. The finite element analysis is used to estimate the parameters of the low-order model. The numerical analysis provides a tool for both designing the actuator and testing the control algorithms. In the thesis, a control algorithm, previously used mainly in active magnetic bearings for compensation of harmonic disturbance forces, is applied by using the built-in force actuator. In the simulations, the control algorithm is embedded in the numerical analysis. The modelling and model-based control are verified by experiments. A 30 kW two-pole cage induction motor with an extended rotor shaft is used for measurements. The results both from simulations and experiments show that, by using the built-in force actuator, the model-based controller is suitable for flexural rotor vibration suppression in a cage induction machine. In particular, the stable operation at the critical speed of the machine can be achieved by using the methodology presented in this research.