Simple Electromagnetic Force Model for Industrial Rotordynamic Analyses of Electrical Machines

Electromagnetic fields in the air gap of an electric machine produce electromagnetic forces between the rotor and stator. These forces couple the electromagnetic system to the mechanical one. This electromechanical interaction may change the dynamic behavior of the rotor system. To control the rotordynamics of electrical machines, it is important to predict the effects of electromechanical interaction between the rotor and stator. The aim of this paper is to introduce a practical method to include electromechanical interaction in rotordydynamics of electrical machines. This aim is achieved by transforming the frequency response function of the unbalanced-magnetic-pull presenting the electromagnetic forces into the form of electromagnetically induced stiffness and damping matrices. The results calculated by this method were compared to the results obtained by a previous calculation method and experimental results. This comparison confirmed that the prediction capability of the developed method is excellent. Finally, the evaluated stiffness and damping matrices obtained by using the developed method can be easily inserted to the general purpose rotordynamic codes, which means that the effects of electromechanical interaction of real machines can be evaluated in a straightforward manner.