Application of a multiobjective minimization technique for reducing the torque ripple in permanent-magnet motors

The main design parameters of a permanent-magnet motor, which reduce the to tal torque ripple, are determined. A two-step design procedure is utilized. First the geometry of the permanent-magnet rotor is derived by a one-dimen sional field analysis coupled to a multiobjective minimization technique. T he objective function of the minimization is defined as a combination of th e electromotive force harmonic components induced in the stater and of the harmonic components of the air-gap magnet permeance, As a second step, a tw o-dimensional numerical model, solved through a finite element method, is a dopted to further improve the analysis of the magnetic field. This allows t he optimization of the magnet are width and the minimization of the cogging torque, The method described has been used for the design of a three-phase , six-pole, permanent-magnet synchronous motor. Experimental tests have bee n carried out to verify the results obtained by the design procedure.