Effective magnetic path length in Epstein frame test of electrical steels

Abstract

The effective magnetic path length l m for a 25 cm Epstein frame test is studied on the basis of a relevant demagnetizing model and determined by a comparative measurement of dc and ac hysteresis loops at each value of peak flux density B p, with the field recorded by H-coils placed above the mid-section of the limbs or calculated from the magnetizing current. The obtained B p and frequency dependences of l m for testing core loss P s and peak field H p of an electrical steel are explained in terms of differential susceptibility along the measured loops and demagnetizing and eddy-current effects on local magnetization processes.