Three dimensional magnetic field computation by a coupled vector-scalar potential method in brushless DC motors with skewed permanent magnet mounts - the no-load and load results

Abstract

The coupled magnetic vector potential-magnetic scalar potential (CMVP-MSP) method of computation of 3D magnetic fields by finite elements (3D-FE), whose theoretical development and formulation were detailed in a companion paper together with 3D-FE grid developments, is applied here to a brushless dc motor with skewed permanent magnet mounts on its rotor. Results of the CMVP-MSP and 3D-FE computation of the magnetic field and associated motor parameters (emfs and armature inductances) are detailed in this paper. These results demonstrate vividly the three dimensional nature of the computed flux distributions, caused by the torque ripple reduction design employing skewed magnet mounts on the rotor. Experimental evidence supporting the validity of the 3D-FE field computations, through comparison between computed and measured armature emf waveforms is also provided in this paper.