고속구동용 마그네틱 기어의 효율 최적화 및 구조적 강건성 향상에 관한 연구

Abstract

Mechanical gears, which are widely used as power converters, transmit power through the meshing of gear teeth. Tooth meshing inevitably causes noise, vibration, and wear, and the use of lubricant to improve it requires frequent maintenance. In order to improve the shortcomings of mechanical gears, a non-contact magnetic gear has been proposed that transmits power by magnetic force. Magnetic gear has attracted attention as a substitute for mechanical gears as it exhibits low noise, low vibration, and low maintenance, and features that do not break gears when overloaded. Research has been conducted to utilize this advantage of magnetic gears and apply them to super-high-speed supercharging systems in automobiles. However, the magnetic gear has a problem in that the eddy current loss increases rapidly due to the configuration and driving characteristics. In particular, it is required to reduce the permanent magnet eddy current loss. In addition, the current magnetic gear is in the early stages of research, and since the structure has not been formalized, it is necessary to improve the structural stability of the magnetic gear according to the high-speed rotation. In this paper, efficiency optimization and structural robustness improvement for high-speed driving of magnetic gears is shown. First, main design parameters are selected and characteristic analysis including loss and efficiency according to the parameters is performed. In addition, to prevent scattering of permanent magnets at high speed rotation and to analyze the effects of permanent magnet eddy current loss, NdFeB, Nd-bonded, and Ferrite permanent magnets are applied and analyzed respectively to derive the optimal model. Before producing the prototype of the derived model, the robustness improvement of the most fragile pole-piece structure among the magnetic gear structures is studied. A pole-piece supporter referring to the reinforced concrete structure was proposed, and a non-conductive supporter was applied to reduce additional electromagnetic losses. Since Nd-bonded permanent magnet has a cylindrical structure, it can prevent permanent magnet scattering, but a separate magnetizer must be constructed. Accordingly, the characteristics of the magnetization method were analyzed, and a magnetization method suitable for improving the efficiency of the magnetic gear was finally applied. A prototype that synthesizes the analyzed contents have been produced and experimental equipment to perform the performance evaluation of the magnetic gear is constructed. However, since the designed efficiency and the measured efficiency did not match, it represents a process for identifying other losses including mechanical loss. As a result of listing and comparing the components constituting the loss of the magnetic gear, it was confirmed that the final designed efficiency and the measured efficiency matched within 1%. This paper presents the process from the design of high-speed magnetic gear to the production and evaluation. The characteristic change according to the main design parameters of the magnetic gear can be confirmed, and the difference in loss and efficiency according to the permanent magnet material can be confirmed. In addition, a new structure of the pole-piece was shown and the characteristics of magnetization of the Nd-bonded permanent magnet can also be confirmed. The experimental method of magnetic gear and the measurement process for other loss due to leakage flux and mechanical loss can be used as a guideline for manufacturing and evaluating magnetic gear.