Vibro-acoustic modelling of an alternator

In this paper we present the basic approaches to building a sequentially coupled model of an alternator to evaluate the vibro-acoustic response resulting from different excitations, such as engine vibration, rotor imbalance and magnetic forces. Special emphasis is given to the set-up and verification of the three-dimensional (3D) structural finite-element (FE) model for the whole alternator and for the alternator components. The verification of the structural model was carried out using experimental modal analysis (EMA), which was also applied for the estimation of the modal damping and for the structural FE model updating. Special emphasis is given to the evaluation of magnetic noise, generated due to the magnetic force excitation in the alternator To estimate the magnetic forces and their harmonic components a 3D magnetic FE model of the alternator was prepared. Finally, the exciting magnetic forces, calculated for the specific operation conditions of the alternator, were transferred into a structural FE model, where the structural and acoustic responses were calculated and analysed. (C) 2006 Journal of Mechanical Engineering. All rights reserved.