Effects of stress on iron loss and flux distribution of an induction motor stator core

Two nonoriented low-silicon iron cores were compared. The laminations were magnetized as in an induction motor stator core, and the flux density and localized power loss measured at various flux densities using arrays of search coils and thermistors mounted on individual laminations. A uniform static radial stress of up to 4 MPa applied to the outside of the core increased the local loss at all measurement points. The maximum increase was around 35% immediately behind the slots. Generally, a sharp increase occurred at around 2 MPa. The change in power loss can be related to the applied stress, which causes the tangential component of flux density to decrease behind teeth and increase behind slots. As a result, the applied stress makes the loci of spatial flux density more circular behind the teeth and more elliptical behind the slots. Localized harmonic components of flux density were generally increased in both cores when stress was applied