Magnetostriction and its contribution to noise in a PWM inverter fed induction machine

PWM inverter fed induction machines generate significant noise. The noise comes not only from radial air gap forces but also from magnetostriction. It turns out that magnetostrictive and radial air gap forces have about the same magnitude in medium sized induction machines. A FEM model, based on actual magnetostrictive data for electric steel sheet, has been derived for calculation of magnetostrictive deformation of the stator. The FEM model has been verified on a test machine in which the radial air gap force is eliminated. Measurements with the test machine connected to a PWM inverter reveal the same spectrum as from standard PWM inverter fed machines. Thus there is reason to believe that noise comes from magnetostrictive deformation and not from magneto acoustic emission (MAE)