복합 연자성 재료를 이용한 고속 영구자석 전동기의 3차원 형상 최적설계

Abstract

High-speed motors are being used in many applications, such as machine tool spindles, aerospace, centrifugal compressors, vacuum pumps, vacuum cleaner, dust collector, friction welding units, turbine generators, and so on. Compared to the conventional general-purpose motors, the major advantages of high-speed motors are smaller size under a given power, higher power density, smaller moment of inertia, fast response, and the ability to be directly connected with other high-speed mechanical device without gear. Core loss of high-speed motors with high operating frequencies is much greater than other losses and is the main source of heat. It is known that a considerable amount of the total core loss in the stator core of a rotating electrical machine is caused by the rotating magnetic field. In the past, an ultra-thin non-oriented electrical steel sheet for high-frequency has been used as to minimize this core loss. However, since the ultra-thin non-oriented electrical steel sheet for high-frequency is expensive, it has the disadvantage of increasing the production cost of the motor. To overcome this disadvantage, a soft magnetic composite (SMC) is used, wherein the magnetic powder is coated with an electrically insulating layer Compared to the traditional electrical steel sheet, SMC materials have the following advantages. First, SMC materials are in general, magnetically isotropic because of their powdered nature, and are therefore suitable for the construction of electrical machines that are subjected to 3-D magnetic fluxes and have complex structures. This isotropic magnetic property results in crucial design benefits and allows magnetic circuits to be designed with 3-D flux paths. Second, SMC materials are manufactured as modules for the core of the motor and hence, they are suitable for motors with complex structures. In addition, the core can be made by a press-molding process, which makes mass production easy. Third, the iron particles are insulated by a surface coating and an adhesive used for composite bonding; the eddy-current loss is much lower than that in laminated steels, especially at higher frequencies; and the hysteresis loss becomes the dominant component of core losses. These properties allow the machines to operate at higher frequencies, resulting in reduced machine size and weight. Fourth, since the SMC materials are cheap, their use can significantly reduce the material costs. Fifth, SMC materials are easy to recycle and finally, alloy powders such as Fe-Ni, Fe-Si, Fe-P, and Fe-Si-Al, which are important as admixtures or for the special application of these composites, can sometimes be used. Therefore, in this paper, a motor is designed by using electrical steel and SMC, a non-linear finite element method (FEM) based on 3-D numerical analysis was used to conduct basic design and characteristics analysis. A prototype was manufactured and characteristics experiment was performed to verify the designed the high-speed permanent magnet (PM) motor. Moreover, 3-D stator topologies are proposed that use the advantages of SMC to improve the efficiency of the motor.