Quantitative Reliability Study of a Motor System and Its Key Components used in Electric Vehicles

• Main Authors: Chang-Shen Lu, 盧長甡
• Other Authors: 吳文方
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/33021269692133161298

碩士 === 國立臺灣大學 === 機械工程學研究所 === 104 === A motor system having key components of a stator, a rotor, a shaft and bearings is studied in this thesis. Special attention is paid to the quantitative reliability of the system and its components. With regard to the stator, accelerated life testing data are collected under various accelerated temperatures and insulation levels. The life distributions and reliabilities of the stator under different insulation levels but normal operating temperature are evaluated based on Arrhenius model. For the rotor and shaft, the influence of rotational speed on the reliability of motor is studied. The reliability issue arises from uncertainties of size and material properties of the rotor and shaft, which results in uncertainty of the critical speed and hence the reliability of the motor. Finite element analysis and the first-order reliability method are employed therein. As for bearings, three different kinds of bearing are discussed but special attention is paid to the reliability evaluation of ball bearings which are frequently used in motors of electric vehicles. After investigating the reliability of each key component, the reliability of the motor is discussed from system point of view. A motor at its design stage and to be used for electric vehicles is considered a role model for the above analyses. The result reveals that the mean time to failure of the motor is acceptable. It is also found from sensitivity analysis that the most important parameter that influences the critical speed of the motor is the part of shaft embedded in the rotor. The adjustment of its length would let the motor avoid its critical speeds and increase its reliability significantly.