METHOD OF MEASUREMENT OF THE NATURAL FREQ UENCIES AND DAMPING FACTORSOF PERMANENT-MAGNET SYNCHRONOUS MACHINES

The vibratory behaviour of permanent magnet synchronous machines depen ds on the modal characteristics of the mechanical structure of their s tator (natural frequencies, damping factors, modal shapes). In this pa per, a novel method, to determine experimentally these characteristics , is presented. First, the classical technics used to measure the moda l characteristics are presented. A theoretical study establishes a rel ation between the supply currents and the vibrations deriving from ele ctromagnetic phenomena. According to this study, an experimental metho d, which enables to determine the natural frequencies and the damping factors of the stator mechanic structure, is proposed: it is carried o ut with the rotor at standstill and uses the forces produced by the su pply currents as excitation sources for the mechanical structure. In o rder to validate the proposed method, it is brought into work on an ex perimental bench and the results are compared to the ones obtained fro m the classical method using hammer excitations.