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

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.