Electrical machine acoustic noise reduction based on rotor surface modifications

Paper in proceeding, 2017

© 2016 IEEE.Electromagnetic acoustic noise from electrical machines has increasingly become an area of attention for both academia and industry. In electric propulsion systems, this is a main contributor to the total acoustic noise and it is usually perceived as annoying due to its tonal appearance. This paper presents an alternative rotor design for a permanent magnet synchronous machine with the objective to decrease prominent machine orders in the acoustic noise by force density harmonics minimization. Apart from this, torque characteristics and core losses are included in the study as well, in order to investigate possible adverse effects. In the proposed design, irregularities are introduced in the rotor surface to suppress harmonics in the flux density by locally altering the airgap permeance. The analysis is based on finite element modelling, using a sequentially solved, weak coupled, multi-physics approach which enables separation of the electromagnetic-, structural dynamical- and acoustic problems. The results show that the most prominent harmonics in the acoustic noise can be reduced without significantly deteriorating the dynamic performance. It is also demonstrated that the core losses of the machine is positively affected by the obtained harmonic magnitude reduction in the flux density. Although the paper focuses on minimization of radial force density harmonics, the results indicate that the approach and the methodology may also be used for torque harmonics minimization.