小型轉軸渦電流減振系統之開發與特性探討

Development and Characteristic Study of a Small Rotor Eddy Current Damping System

周尚德(Budi Prajna)

指導教授 ： 黃光裕

國立臺灣大學/工學院/機械工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.00157

摘要

當一導電體受到一時變磁通量時，在導電體中即會產生渦電流，渦電流會產生與時變磁場磁極方向相反的磁場(二次磁場)，磁場的相互作用即產生抵抗磁場變化的力量。藉由導電體的電阻，會將渦電流以熱損耗方式釋出，如此則可以消耗掉意圖改變磁場之振動動能，而達到減振的效果。本論文的研究目的在於設計製作可靠且高性能的轉軸渦電流減振系統，使其能滿足小型轉軸在偏擺時所需要的減振功能。首先彙整參考文獻及探討轉軸渦電流減振的作用原理，並在評估許多設計參數與變異性之後，從而進行轉軸渦電流減振系統的實體設計以及組裝。本論文同時從理論模型以及有限元素模型的分析，了解各個設計參數對於渦電流減振作用的影響。接著對所完成的轉軸渦電流減振系統進行動態特性的測試，以減振力、阻泥比和減振時間常數來評比減振系統之性能表現。在提升減振系統的性能上，提出了雙環形磁石排列方式以及環形Hallbach磁石排列方式，可以提升減振效能使阻尼比2~4倍，另外對也提出渦電流限轉磁石配置方式，可以改善高轉速不穩定現象。

關鍵字

渦電流減振 ； 小型轉軸 ； 多樣化設計 ； 效能評比 ； 實驗與分析

並列摘要

When a conductive material is subjected to a time-varying magnetic flux, eddy-currents are generated in the conductor. These eddy-currents circulate inside the conductor generating a magnetic field of opposite polarity as the applied magnetic field. The interaction of the two magnetic fields causes a force that resists the change in magnetic flux. Due to the internal resistance of the conductive material, the eddy-currents will be dissipated into heat, consuming the kinetic energy of the vibrating element, the conductor or the magnet, which causes the time-varying magnetic flux, and thus producing a damping effect. The aim of this thesis is to develop a reliable and high performance of rotor eddy-current damping system which satisfies the damping capability needed to absorb the lateral vibration of small rotating machinery. This thesis will first investigate and analyze numerous literature surveys on working principle of rotor eddy-current damping. The thesis then advances to estimation of numerous design factors and variations of fabrication process. Theory model analysis as well as finite element analysis are being used to understand the influence of different design variables on the damping system. Dynamic characteristic testing is applied to evaluate the damping system performance by comparing damping force, damping ratio and damping time constant on various designs. Finally, this thesis proposed a novel double ring magnet arrangement and a novel Hallbach ring magnet arrangement, which improve the damping system performance by increasing the damping ratio by 2~4 times. Eddy-current rotation restriction magnet arrangement is also being introduced which has been proven to greatly improve the instability problems during the high speed operations.

並列關鍵字

eddy-current damping ； small rotor ； variety designs ； performance evaluation ； experiment and analysis

參考文獻

[1] Kronenberg, K., “Quantitative Considerations to Self-Centering Magnetic

[2] Mukhopadhyay, S. C., Ohjj, T., Iwahara, M., and Yamada, S., “Design, Analysis and Control of a New Repulsive-type Magnetic Bearing System,” IEE Proceedings on Electronic and Power Applications, Vol. 146, No. 1, January 1999, pp. 33-40

[4] Baran, W. K. A., “Influence of Different Magnetic Field Profiles on Eddy-Current Braking,” IEEE Transaction on Magnetics, Vol. Mag-6, No. 2, June 1970, pp. 260-263

[5] Nagaya, K.; Kojima, H.; Karube, Y.; Kibayashi, H., “Braking Forces and Damping Coefficients of Eddy Current Brakes Consisting of Cylindrical Magnets and Plate Conductors of Arbitrary Shape,” IEEE Transactions on Magnetics, Vol. 20, No. 6, November 1984, pp. 2136 – 2145

[7] Jang, S. M., Lee, S. H., “Comparison of Three Types of Permanent Magnet Linear Eddy-Current Brakes According to Magnetization Pattern,” IEEE Transaction on Magnetics,