Modeling Electric Motors with High Fidelity for Accurate eDrive NVH Simulation

Abstract

<div class="section abstract"><div class="htmlview paragraph">A sophisticated finite element analysis (FEA) method for modeling interior permanent magnet (IPM) electric motors is presented. Based on this method, a coupled structural-acoustic analysis procedure was developed to simulate the motor dyno vibroacoustic responses with improved accuracy and reliability for NVH (noise, vibration, and harshness) behavior prediction over a wide range of torques and frequencies under the operational electromagnetic forces. The proposed motor modeling and analysis method is detail-oriented with high fidelity in modeling the structure and complex material representation. To effectively deal with the motor stator core constructed with large numbers of electromagnetic laminae, the unit-cell approach was employed to derive the core material properties by homogenizing the laminated core as an equivalent orthotropic material. Meanwhile, the windings were modeled by capturing the precise geometry for accuracy improvement. Additionally, the method facilitates modeling the varnish fill details between the core, linings, and the windings, such as bonded locations, area coverage, and fill rate. Guidelines pertinent to FEA modeling of motor components related to element type selection, mesh size determination, acoustic domain definition, and structure-acoustic interface connection are also provided. The stator analysis model was first correlated with the free-free modes and frequency response functions (FRF) obtained from the vibrometer test before being incorporated into the motor dyno system to simulate the radiated noise for critical motor whine orders and other NVH-related behavior. Finally, the simulated results were verified against motor dyno test data over a wide range of torque and frequency. This high-fidelity motor model can further be used for advanced studies in objectively assessing the influence of airgap eccentricity, rotor skew configuration, stator attachment architecture, etc., on motor NVH behavior.</div></div>