Magnetostriction characteristics of 3.1% grain-oriented silicon-iron transformer steel

Abstract

An apparatus has been developed for the measurement of the a.c. magnetostriction of laminations of transformer steel subjected to a 50c/s excitation. The apparatus employs a ceramic displacement transducer and is capable of measuring a.c. displacements in the range 10⁻⁴–10⁻⁸cm. Data are presented on the observed variation of magnetostriction, core loss and permeability with mechanical stress. It was found that the magnetostriction coefficient of 46-grade oriented transformer steel, in the fully annealed state and at a peak induction of 15000Gs, is usually negative and has a median measured value of −3.0 × 10⁻⁷.