Effect of Si Content on Iron Loss of Electrical Steel Sheet Under Compressive Stress

The magnetic properties of nonoriented electrical steel sheets under compressive stress were investigated. Iron loss under compressive stress decreases with an increase of Si content. In particular, a 6.5% Si steel sheet shows an extremely low deterioration ratio of iron loss under compressive stress. Furthermore, the deterioration ratio of a 6.7% Si steel was negative. These results were explained well by magnetostriction. The deterioration ratio of iron loss under compressive stress decreases with a decrease of magnetostriction. To evaluate the effect of magnetostriction on iron loss in a motor, interior permanent magnet motors were made using 3.0%, 6.5%, and 6.7% Si steel sheets. In the motor using 3.0% Si steel, the iron loss was increased after the heat shrinking. On the contrary, in the motor using 6.5% Si steel, the iron loss showed a little change after heat shrinking and in the motor using 6.7% Si steel, the iron loss decreased after the heat shrinking.