A simplified approach for accurate estimation of transverse magnetic forces in micro-actuators having inclined pole faces

This paper proposes a fringing range method for accurately evaluating transverse magnetic forces in micro-actuators having inclined pole faces. In this method, the fringing Bur in an air gap is assumed to be uniformally distributed in a range that is represented by a fringing coefficient, which is then adjusted systematically to ensure the magnetic forces are accurately determined under defined conditions of actuator physical symmetry. Although this approach can be generalized to other cases, this paper focuses on its application to the case of semi-infinite inclined pole faces. It is shown that the fringing range method can be used with good accuracy if the pole thickness is much larger than the air-gap length. This method was applied in designing a micro magnetic bearing actuator whose diameter is 2.6 mm.