Development Policy of SMC to Improve Efficiency of Axial Gap Motor Employing Coreless Rotor Structure

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 that of conventional radial gap motors (RGMs). In general, AGMs employ the soft magnetic composite (SMC) for the stator core since they have three dimensional magnetic paths unlike RGMs. If AGMs employ the SMC which has low iron loss characteristic, the efficiency can be improved. On the other hand, the average torque is decreased because the SMC basically has tradeoff-relationship between the iron loss characteristic and the permeability. Hence, in this research, an AGM having coreless rotor structure that torque performance is not easily affected by the permeability of the SMC is proposed. In this paper, many virtual SMC materials which have different iron loss and permeability are considered for the proposed AGM employing the coreless rotor structure. Finally, suitable SMC characteristic to enhance the efficiency over a wide operating range is revealed by three-dimensional finite element analysis (3D-FEA).