Direct approach in performance calculation on permanent-magnet DC motor

Direct approach avoids some derivative operations in field and torque calculation. The accuracy of magnetic field calculation in presence of ferromagnetic and permanent magnets using finite element method was improved. The subparametric finite elements were used and vector potentials at Gauss points were calculated with the residual O(h(3)). A higher accuracy was also achieved at vertex and midside nodes of the mesh. The electromagnetic torque was calculated directly from magnetic vector potentials of moving conductors. The procedure was compared with two recent methods. The agreement with test results of a PMDC motor was improved.