An approach to modelling of magnetically excited forces in electrical machines

A distinction is made between the vibrations produced by the fundamental current supplying the machine and the much smaller higher harmonic currents, with frequencies ranging into the kilocycles range. The small harmonic currents are emphasized. An appropriate mathematical modeling technique is presented. A mechanical model is selected based on modal analysis techniques. A method is developed for finding the driving force for each mode shape. This is illustrated with measurements on a permanent magnet machine. Experimental verifications of the model show the importance of a correct knowledge of eigenfrequencies and damping coefficients