Abstract
Rotors are important part of permanent magnet high speed traction motor used in electric vehicle. These rotors are subjected to varying speed and torque loads. Usually electromagnetic performance demands thinner rotor lamination dimensions which conflicts with the mechanical performance requirement like maximum possible rotation speed and fatigue life. Hence estimation of rotor fatigue life is very crucial at design stage to have tradeoff between mechanical and electrical performance. This paper is focused on method to estimate rotor fatigue life using FEA tools and case study of one of rotor failure problem solved using this technique. In the present work, stress based analysis approach is used to estimate fatigue life. A single rotor lam with plain stress behavior is used for estimating rotor stress and S-N curve derived from cyclic uniaxial load is used. This approach of estimating fatigue life of rotor was applied to improve the fatigue life of rotor failed in product validation test. Several design modification iteration coupled with rotor life estimation were proposed and best design was selected. Fatigue life was estimated to be infinite and same was confirmed during test of modified rotor. Though, there was no exact match of fatigue life between test and estimation, good trend was observed between two. Fact remains that, this process would have existed earlier then costly design changes and time could have been saved. Since fatigue life is geometry dependent, predicted life with help of S-N curve of standard specimen is not exact life of rotor lamination and results need to be verified with test data. Though in the absence of lot of literature for rotor fatigue at this point of time, integration of this method into early stage of product development can lead to save cost and time associated with product development.