Punching effects on local magnetic properties near the edge of nonoriented electrical steels

Purpose The purpose of this study is to investigate the effect of punching on the local magnetic properties of the nonoriented electrical steel sheet. Design/methodology/approach A microcomposite B-H sensor consisting of a pair of B probes with a spacing of 2 mm and a 1.8 x 1.8 mm(2) H coil is designed. The region and degree of local magnetic properties degradation caused by punching can be quantitatively analyzed by flexibly moving the composite B-H sensor. The influence and physical mechanism of punching on the hysteresis loss, eddy current loss and excess loss are analyzed based on the Bertotti loss separation theory. Findings This study investigates the deterioration effect of the punched nonoriented electrical steel. The permeability near the edge decreases, and the core loss as well as the microhardness increases. The region of magnetic property deterioration is dependent on the area of work hardening. Originality/value The microcomposite B-H sensor can be used to measure the magnetic properties near the edge of electrical steel sheets under different processing conditions. This study provides the possibility of precise magnetic property model of the motor core after punching, especially valuable for motors without annealing process.