A Simulation Strategy for Dynamic Response of an Electric Drive Stator

Electric vehicles are ushering in a new era of travel that transform transportation and shape the future of mobility. The transition to electric vehicles requires development of new methodologies that effectively interpret and simulate the complex systems in these vehicles. The electric drive is one such system and constitutes a critical component for the electrification of vehicles. In design & development of such an electric drive, a stator vibration durability test was performed and observed that the varnish level on the stator might impact the durability of stator assembly. To analyze this behavior computationally in Finite Element Method (FEM), a simulation strategy for evaluation of dynamic response of an electric drive stator is developed. The simulation method uses the Abaqus/Standard finite-element solver code and utilizes linear dynamics capabilities along with a submodeling technique. In an electric drive, the stator core is the stationary part of the system. It is made of thin metal sheets stacked and fastened together. In the FEM described here the stator core is modelled directly with a laminated structure. Abaqus cohesive elements are used to model the interfaces in the laminate structure of the stator core. The other component is winding that passes through the stator core. The interaction between stator and winding is governed by the varnish coating. This interaction is also captured with cohesive elements. The global model represents the complete stator structure. The global analysis is a two-step simulation. The first step is modal analysis uses the Abaqus AMS eigenvalue solver with damping projection. The second step is a mode-based steady-state dynamics procedure. The parameters that greatly affect the dynamic response of the stator are the traction stiffnesses and the damping values in the cohesive elements. These can be adjusted to shift the natural frequency and increase or decrease the peak acceleration levels. The submodel represents a small portion of the stator structure. It has a finer mesh to better predict critical stresses in the cohesive elements. It is a one-step simulation using the direct steady-state dynamics procedure. The boundary of the submodel is driven by displacements interpolated from the global model results. To understand the impact, this study is carried out on two set of varnish levels, a partially varnished (30% connection length) and fully varnished (100% of connection length) models. The partially varnished submodel shows substantially higher stress compared to the fully varnished submodel. Thus both simulation and physical testing indicate the connection between the stator core and the pins is an important structural component of the stator assembly. This strategy provides the simulation approach other than homogenization to model laminated structure and the interaction in linear dynamics. Submodels can be constructed for any portion of the stator assembly to evaluate adequate varnish level. With additional testing and parameter calibration studies quantitative evaluation of durability can be possible.