An Elastic Rotor Model for High-Speed Electrical Machines with Active Magnetic Bearings

A program for modelling elastic rotor dynamics in active magnetic bearings has been made for PC-Matlab. The kinetic and potential energy integrals are diskretized and an equation of motion is obtained in a matrix form. Active magnetic bearing dynamics can be included in the matrix equation. From this matrix form the critical speeds, eigenfrequencies, mode shapes, unbalance responses and frequency responses can be calculated. A low order model for control system design purposes can also be calculated by modal analysis. The validity of the model is studied by comparing the calculated eigenfrequencies and eigenmodes with the analytic solutions of the Timoshenko beam equation. The program is also verified by testing real high speed rotors. The measurements are in a good agreement with the calculations.