Numerical prediction and analysis of electromagnetic vibration and noise of claw pole alternator

Abstract

With the improvement of internal combustion engine noise, the noise of claw pole alternator which is universally used on modern automobiles is becoming more distinct. Extensive experimental results show that the noise of claw pole alternator is annoying at low to middle speed and mainly originates from the electromagnetic noise. In this paper, a complete methodology for electromagnetic vibration and noise prediction of claw pole alternator is presented. It is a three-step multiphysics simulation. The first step is to calculate the magnetic force exerted on the inner surface of the stator using 3D FEM. The second step is the structural analysis, which is to investigate the natural resonant frequencies and modal shapes of the alternator system taking into account the real mechanical boundary conditions. The third is the electromagnetic vibration and noise calculation by using modal superposition method and boundary-element method, respectively. Simulation results agree well with those measured by experiments. Furthermore, the mechanisms of electromagnetic vibration and noise are analyzed by using the electromagnetic theory. The method can be used in the initial design stage of claw pole alternator and is also suitable for other types of motor.