Optimal excitation of permanent magnet synchronous machines via direct computation of electromagnetic force components

Vibration of the stator along with pulsation of the electromagnetic torque on the rotor are known as sources of acoustic noise in permanent magnet synchronous machines (PMSMs). Magnetic design and stator excitation can be tailored to mitigate undesirable vibrations which are viewed as byproducts in electromechanical energy conversion process. In this paper, using direct computation of the radial and tangential components of the electromagnetic force in the airgap of a PMSM, stator excitation for elimination of various force harmonics is presented. The proposed method is based on a field reconstruction method that rapidly calculates the radial and tangential flux density and force components under arbitrary stator excitation. Using the field reconstruction method, stator current waveforms that minimize the ripple of both torque and radial force are derived subject to the constraint of maintaining a satisfactory level of torque density