Investigation of Development Policy of SMC Material for High Efficiency over a Wide Operating Range in Axial Gap Motors Having Coreless Rotor Structure

Abstract

　In recent years, electric motors having flat shape are desired in order to minimize system size as well as enhancing the efficiency. Therefore, axial gap motors (AGMs) have attracted significant attention because they can achieve higher torque density in flat shape than conventional radial gap motors. In general, AGMs employ Soft magnetic composite (SMC) for stator core since they have three dimensional magnetic paths. If AGMs employ SMC which has low iron loss characteristic, the efficiency can be improved. However, average torque is decreased because SMC basically has tradeoff relationship between iron loss characteristic and permeability. Hence, in this research, AGM having coreless rotor structure that torque performance is not easily affected by the permeability of SMC is proposed. In this paper, many virtual SMC materials which have different iron loss and permeability is considered for the proposed AGM. Finally, suitable SMC characteristic to enhance the efficiency over a wide operating range is revealed by three-dimensional finite element analysis (3D-FEA).