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

• Main Authors: Budi Prajna, 周尚德
• Other Authors: 黃光裕
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/47678007125031579529

碩士 === 國立臺灣大學 === 機械工程學研究所 === 93 === 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.