Magnetically Oriented Core Lamination Manufactured from Non-Oriented Electrical Steel Sheets

Soft magnetic cores of electric motors and generators are normally manufactured by stamping individual circular laminates from non-oriented electrical steel (NOES) sheets and stacking them layer by layer to reach the required height. The traditional lamination method can only achieve the average performance of the NOES since the magnetization is in all the directions of the sheet plane. Although NOES is ideal to have isotropic magnetic properties in all the directions of the sheet plane, commercially available electrical steel sheets always show apparent anisotropy in the rotating magnetization directions lying in the sheet plane. The anisotropy in magnetic properties not only causes fluctuations in the rotating magnetic field, but also leads to oscillations in electromagnetic torque, and thus needs to be minimized. In this paper, a novel electrical steel lamination technique is developed, which takes the advantage of the inherent magnetic anisotropy of electrical steel sheets to improve the motor performance by aligning the teeth of the laminates to the electrical steel sheet’s easy magnetization direction while significantly reducing the material waste during the lamination process. This technique differs from the slinky or spiral lamination technology in that individual laminates (instead of a continuous, spiral lamination) are stacked which can significantly reduce the eddy current loss by isolating the individual laminates as in the conventional method. The process to manufacture prototype lamination cores from commercial NOES sheets using this new method is demonstrated in this paper. The potential impact of this manufacturing technology on the motor industry is discussed.