Domain Refinement Techniques For Improved Magnetic Properties Of High Permeability Grain Oriented Electrical Steel

Domain refinement techniques have been used for the reduction of transformer core losses for some 15 years. A novel method is described which uses a ball indentation technique. This particular method can reduce the average loss of grain oriented 3.15%Si electrical steel by 5-10%, without applying excessive pressure and damaging the physical integrity of the product. The load applied to the ball unit to induce domain refinement is critical in determining the performance. The final loss achieved on material using the technique was found to be proportional to the measured peak induction. This relationship enables the producer of domain refined material to predict the posttreatment loss level, enabling selection of suitable material for commercially viable domain refinement. Ball unit domain refinement also reduces the wide loss variation observed in the initial material. Therefore, the overall commercial yield of the material increases. Two prototype devices proposed for industrial implementation of 'ball unit domain refinement' are also described: an indexing device and a continuously circulating ball unit device.