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This paper proposes an axial-flux permanent magnet machine (AFPM) that uses a neodymium-bonded permanent magnet (Nd-bonded PM) and a coreless rotor structure and assesses how it performs in industrial applications requiring high efficiency and low cost. The AFPM is able to achieve high efficiency in high-speed regions because its Nd-bonded PM can restrain eddy current loss. Additionally, the AFPM can continuously function at the rated operating point without a cooling system, so the expenses for one can be eliminated. Hence, the AFPM can simultaneously achieve high efficiency and low-cost mass production. In this paper, a comprehensive comparison including the thermal characteristics of the proposed AFPM and a conventional radial-flux permanent magnet machine (RFPM) is shown. Furthermore, this paper also focuses on how the aspect ratio influences the thermal characteristics of both machines. Finally, the effectiveness of the proposed AFPM in industrial applications is assessed using 3D-FEA and experimental results.

This study aims to improve the torque performance and manufacturability of axial-flux permanent magnet (AFPM) machines. Hence, we propose a novel AFPM machine that employs a soft magnetic composite (SMC) core with tooth-tips constructed by a one-pressing process and die. In this paper, the proposed AFPM machine is compared to two conventional AFPM machines using an SMC core. One of them has open-slot structure without tooth-tips. Another model employs an SMC core with tooth-tips pressed by a conventional pressing process that requires multiple operations and dies. As a result of the comparison, the proposed AFPM machine realizes a much higher torque than the two conventional machines. Additionally, the manufacturability of an SMC core with tooth-tips pressed by the proposed method is superior to the conventional one because the proposed structure can be realized by the one-pressing process and die. Furthermore, two prototypes of the proposed AFPM machine and the conventional one with an open-slot structure are fabricated, and then, they are compared by experiments. Consequently, the proposed AFPM machine achieves a 15.7% higher torque than that of the conventional machine using an open-slot structure. Finally, this paper presents an improved design of an AFPM machine with SMC cores using the proposed pressing process. As a result, the proposed AFPM realizes a 20% larger torque than that of a conventional model employing an open-slot structure.

In recent years, there has been growing demand for flat electrical machines in order to minimize system size while also maintaining high efficiency. In general, axial flux machines (AFMs) are more suitable for flat form than radial flux machines (RFMs). AFMs usually employ a soft magnetic composite (SMC) for the stator core, and their efficiency can be improved by employing an SMC that has low iron loss. However, this reduces the average torque because there is generally a tradeoff relationship between iron loss and magnetic permeability in SMCs. This article, therefore, proposes an AFM with a coreless rotor structure in which the torque performance is not easily affected by the permeability of the SMC. This article aims to reveal the ideal SMC characteristics for high efficiency in AFMs. First, many virtual SMC materials with different iron loss and permeability are used for simulations of AFMs in order to investigate sensitivity to material properties. The simulations by virtual SMCs take into account the experimental increase in the iron loss. As a result, guidelines for developing SMCs are constructed based on the experimental results. Finally, prototype AFMs employing new SMCs developed by following the guidelines are shown, and it is found that they offer higher efficiency in all operating area than conventional AFMs. In particular, one prototype achieves an extremely high efficiency of over 96% at 6000 r/min, 0.8 Nm in experiments.