Analytical modelling and finite element computation of radial vibration force in fractional-slot permanent magnet brushless machines

Abstract

Analytical models have been developed for analysing the radial vibration force in fractional-slot permanent magnet machines and validated extensively by finite element analyses. They are used to investigate the influence of (a) stator slotting, (b) tangential field component, (c) radius in the airgap for computation, and (d) load condition etc. on the radial vibration force calculation. The major findings can be summarised as follows. (1) Even on open-circuit, the low harmonic component (e.g. 2 nd for 10-pole/12-slot machine, and 1 st for 8-pole/9-slot machine) of radial force exists due to slotting effect although the amplitude is relatively low, while the slotless analytical model cannot predict this phenomenon; (2) However, on load, slotless analytical model is accurate enough in the radial force analysis, since in this case, the low order harmonic component of radial force is mainly due to the interaction between the magnet field and the armature reaction field, and is largely determined by the combination of pole and slot numbers; (3) It is much more reliable to calculate the radial force in the middle of airgap, rather than close to the stator bore, while the harmonic contents of radial force are almost independent of radius in the airgap; (4) The simple formula accounts only for the radial field component in the middle of airgap is accurate enough for radial force calculation.

Comparison of PM machines with concentrated windings for automotive application

“…These unwanted harmonics cause negative effects, such as localized core saturation, eddy current losses in the magnets [1], [2], noise and vibration [3]- [5], which are the main drawbacks of these windings. To overcome these disadvantages several methods have been developed and investigated in the last period of time [6]- [8].…”

Low Space Order Analysis of Radial Pressure in SPMSM With Analytical and Convolution Approaches

“…Indeed many contributions of specific effects linking the interactions between armature, rotor and permeance effects are combined. In [7] and [8] the author gives different contributions for each harmonic of the pressure but without a slotting effect, in the case of synchronous machines with magnets (IPM and SPM).…”

Improved Method for Calculating Armature-Reaction Field of Surface-Mounted Permanent Magnet Machines Accounting for Opening Slots

“…The magnetic field is one of the most important issues in the permanentmagnet machines. It influences the performance of the motor such as torque ripple [4], armature winding inductances [5,6], acoustic noise and vibration spectra [7], radial force distribution [8,9], etc. Its accurate prediction can significantly facilitate and expedite their optimal design in terms of efficiency, compactness, cost and reliability.…”