Virtual Evaluation of Stator Failure Modes using Multiphysics Analysis Approach

The modern luxurious electric vehicle (EV) demands high torque and high-speed requirements with increased range. Fulfilling these requirements, arises the need for increased electric current supply to motors. Increased amperage through the stator causes higher losses resulting in elevated temperature across the motor components and its housing. In most of the cases, stator is mounted on the housing through interference fit to avoid any slippage during operation conditions. High temperature across the stator and housing causes significant thermal expansions of the components which is uneven in nature due to the differences in corresponding coefficient of thermal expansion (CTE) values. Housings are generally made of aluminium and tends to expand more having higher value of CTE than that of steel core of stator which may give rise to a failure mode related to stator slippage. To address this slippage if the amount of interference fit is increased, that’ll result in another failure mode related to durability of the stator and housing at low temperature condition due to higher contraction of aluminium housing. Spatial distribution of temperature across the motor components, subjected to different types of losses is very critical to analyze the failure modes and multiple complex simulations are required to predict that. In this paper, we are exploring the effect of high amperage through the hairpin with the help of a simplified coupled electro-thermal analysis. The spatial temperature distribution obtained through this analysis is imported into a thermo-structural analysis to obtain the deflection and stress developed within the stator components and housing. Predicted deflection can give an insight into the slippage failure mode at the stator-housing interface. Additionally, the durability of different stator components can also be evaluated subjected to the amperage fluctuation during operation conditions. Hence, the finite element (FE) based multiphysics simulation methodology described in this paper can be used as a decision-making tool in the initial design phases to avoid any slippage and durability related failure modes of stator components.