Eiji Shimomura

Effects of external stress on magnetic properties in motor cores

The effects of shrink fitting on the magnetic properties of iron cores are investigated in order to simulate the magnetic behavior of iron cores mounted in motor frames. Shrink fittings, of course, decrease permeability and increase effective magnetostriction and magnetic loss. It is well known that the magnetostriction increment and the permeability decrement are explained by the increase of magnetoelastic energy due to compressive stress by shrink fitting. The magnetic loss increases, however, cannot be explained by this energy. We demonstrate experimentally that the magnetic loss increases result from mechanical work due to the magnetostrictive movement of the iron core under compressive stress.