Compensation of permanent magnet motors torque ripple by means of current supply waveshapes control determined by finite element method

A method for determining the supply current waveshapes for torque ripple compensation in permanent-magnet motors without saliency and damping bars, by means of a finite-element code, is presented. First, a theoretical analysis shows that current waveshapes producing constant torque can be determined. This analysis leads to an expression for the current as a function of the motor EMF (electromotive force) and cogging torque. Several methods, based on finite-element computation of the magnetic field, for computing the cogging torque and EMF are proposed and compared. A special experimental bench for motor torque measurement is used to validate the theoretical results