Correlation Between AC Core Loss and Surface Magnetic Barkhausen Noise in Electric Motor Steel

Core loss is a significant source of energy loss in electric motor steel laminates. Therefore, there is interest in monitoring the quality and consistency of laminates at various stages of manufacturing. The purpose of this study was to investigate the feasibility of using surface magnetic Barkhausen noise for the evaluation of AC core loss, and further, to examine potential origins of magnetic loss in non-oriented electrical steel. Core loss values were measured by a single sheet tester and Barkhausen noise measurements were performed using pole flux control on eight laminates with various grain size, texture and composition. Magnetocrystalline energy was calculated from X-ray diffraction data to quantify texture. Results demonstrated higher surface Barkhausen emissions for samples with lower core loss. Barkhausen noise analyses were used to examine the interplay among core loss, grain size, magnetocrystalline energy and B–H characteristics. The inverse correlation between core loss and Barkhausen noise emissions was qualitatively explained in terms of the orthogonal vector contribution of microscopic eddy currents to losses associated with bulk currents arising in the sample during magnetization.