Comparison of vibration and magnetic force behaviours between different switched reluctance machine topologies

Switched reluctance machines (SRM) are widely accepted to have higher acoustic noise emissions than other machine technologies. Their acoustic noise becomes a crucial drawback for their penetration into the many applications which are noise and vibration sensitive. The poor sound quality of SRMs results from vibration of the stator structure, caused by excitation of high magnetic radial forces in the air-gap. Loud noise occurs when the radial forces on the stator pole excite natural frequencies of the stator structure, leading to high stator vibration. This paper compares and investigates the magnetic force, mechanical vibration and acoustic noise behaviours using a multi-physics analysis of different SRM topologies: I) A 12/8 conventional SRM, II) A 12/8 segmental rotor SRM and III) A 12/10 single-tooth wound segmental rotor SRM. The magnetic force densities which are the major source of vibration are calculated by 2D magnetic Finite-Element (FE) simulation at the same output power. These force densities are applied as input to the 3D structural FE simulation to calculate the vibration motions, and to predict the acceleration, velocity and deformation of the SRM structure. The acoustic noise emission is computed by 3D Boundary Element Method (BEM) using the vibration data results obtained by 3D structural FE. The simulation results for the SRM topologies are compared and discussed.