Schwingungen von Ständern elektrischer Groβ-Maschi

The natural frequencies of the stators of large electric machines are calculated as equivalent rings, inserting the total moment of inertia of the ring cross-section and not only that of the active iron. To excite these it is not only necessary for the forcing frequency to be in tune but there must be a certain spatial distribution of the acting forces corresponding to the required amplitude distribution in space. Otherwise, resonance does not occur. Treating the stator supposed rigidly held as a pair of circular segments gives good agreement with measured values.