Accurate Modal Analysis Method for Automotive Drive Motors Considering Composite Structures and Impregnating Windings in the Design Phase

The medium-thickness shell theory (MST) has been widely used to calculate the natural frequencies of the stator system. However, the first-order shear deformation theory (FSDT) in structure and the simplified constitutive equation in material will make MST cause errors. Moreover, the structural simplification and inaccurate prediction of anisotropic material parameters (AMPs) further deteriorate the computational accuracy. To reduce errors, a forward analytical calculation method (FACM) for modal analysis of the stator system is proposed. This FACM can reduce theoretical errors and structural simplification errors and can take the effect of impregnating windings into account. First, the solid element model is proposed to replace the medium-thickness shell model (MSM), and the theoretical limitations of the MST can be eliminated. Then, the analytical modeling method for windings is proposed, in considering the structure of windings and the stiffness effect caused by impregnating processes. This method can solve the difficulty in calculating the natural frequencies of the stator system with impregnated winding. Afterward, a forward calculation method (FCM) for AMPs of the stator assembly based on the unit cell is proposed, which can accurately predict AMPs without modal experiments. Finally, the accuracy of the FACM is verified by modal experiments, and the maximum relative error is 3%.