AN IMPROVED APPROACH TO POWER LOSSES IN MAGNETIC LAMINATIONS UNDER NONSINUSOIDAL INDUCTION WAVE-FORM

This paper shows that it is possible to accurately predict power losses in ferromagnetic laminations under nonsinusoidal magnetic flux by specifically considering the dependence of hysteresis, classical, and excess loss components (Ph, Pe, and Pe, respectively) on the magnetic induction derivative B. Basically, we assume, through generalization of experimental and theoretical results under sinusoidal induction, that Ph α <Ð BÐ >, p,α <Ð B2Ð> and Pc α <Ð BÐ 3/2> where the brackets indicate averaging over the magnetization period. An analytical expression for total power losses under distorted flux is consequently worked out. It only requires, for a complete prediction, a priori knowledge of one value of Ph and one value of Pc respectively determined by means of a quasi-static measurement and a measurement of total loss in sinusoidal flux at a single test frequency. The uncertainties associated with previous derivations in the literature, consequent to empirical treatment of excess losses, are thus overcome. Experiments are reported concerning grain-oriented, nonoriented and amorphous laminations, with distortion introduced by a variable amount of the third harmonic flux component. The specific case of trapezoidal induction waveform is also considered. It is concluded, from comparison of experiments and theory, that the basic phenomenology of losses under distorted flux can quantitatively be assessed through the present approach. © 1990 IEEE