Prediction of mechanical stress effects on the iron loss in electrical machines

Iron losses can account for a significant portion of the total loss in electrical machines. Nevertheless, although analytical and numerical techniques have been developed for predicting the iron loss density distribution and the total iron loss of various types of machine under any operating load condition, to date these have neglected the effect of mechanical stress. However, during the manufacture of many electrical machines, a significant radial compressive stress can be imposed on the stator lamination stack, by shrink fitting/pressing an outer frame, for example. This paper describes a technique that has been developed for predicting the effect of compressive stress on the iron loss density in lamination materials, and demonstrates its use in calculating the iron loss of a permanent magnet brushless dc motor.