Computation and measurement of magnetically induced vibrations of a switched reluctance machine

The computation of magnetically induced vibrations within an electrical mac hine is a task that presents certain difficulties. Yet, the results of such a computation will be of utmost importance in the magnetic and vibratory d esign of a machine as well as of its power supply. Since the damping term o f a machine assembled on a workbench is practically impossible to predict, as are the sizeable number of coupled phenomena that cause vibrations, ther e is in essence no accurate theoretical model able to compute vibrations du ring the initial design stages of the machine. Moreover, a model that is co mplete, yet cumbersome to implement, does not in general enable the type of parametric studies necessary for developing a complex machine-converter se t to be carried out. In the paper, therefore, the authors have not only ado pted some simplifying hypotheses, but also have combined both theoretical a nd experimental results to construct such a model. The model consists of a mechanical unit which represents the machine modal characteristics and allo ws, in particular, development of a transfer function between the magnetic forces and the stator vibrations. These forces are of a global order of mag nitude and have been computed with the help of a second magnetic unit for w hich it has been assumed that the distribution of stresses exerts no influe nce whatsoever on the acceleration at the stator periphery. A final electri cal unit makes it possible for us to compute the current present in the pha se. The validity of this model is then verified experimentally, and an appl ication example is provided.