Novel Electrical Steel Core Lamination Manufacturing Method

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Laminated electrical steel core is an indispensable component of electric motors. It is required that the magnetic properties of the lamination core be optimum in all the directions of the sheet plane so that maximum efficiency and minimum energy losses can be achieved. This requires that the easy magnetization axes ( for bcc iron) of the crystals be aligned evenly to all the directions in the sheet plane. However, the metallurgical mechanisms governing the formation of the crystallographic textures usually lead to a {111} texture, which does not have the easy axis in the sheet plane. On the other hand, even though it might be possible to produce such a texture (with an intensity of a few times higher than random) in non-oriented electrical steels, it is still very difficult to eliminate other detrimental textures with axes in the sheet plane. Thus, currently, the magnetic properties of the lamination core using non-oriented electrical steel sheets is still far from optimum.

Nevertheless, even in a non-oriented electrical steel without optimum texture, there usually exists a direction (in the sheet plane) in which the magnetic property is better than other directions (up to 20-25% in core loss) . Using the conventional lamination method, i.e. stamping circular laminates from the steel sheets and stacking up the individual sheets to form the core, one could not align all the magnetization directions to the easy axis direction of the steel, thus the magnetic properties of the steel sheets are not optimally utilized. Even for steel sheets with a strong //ND texture, the advantage of the //ND texture is also not completely utilized, since the magnetization directions of the laminate are in all the directions in the sheet plane, not only in the directions with the strongest texture.

A new technology has been developed by this team which is intended to provide a novel lamination core manufacturing technique so that the magnetization directions of the laminates can be precisely aligned to the direction in which the magnetic properties of a textured steel sheet are the best. In this new method, rectangular strips (instead of circular laminates) are first cut from the steel sheets with the short side of the strip pointing to the direction with the best magnetic properties; the strips were then bent to form circular preforms and the ends were joined. The preforms were finally punched to form the circular laminates. In this way, not only can the best magnetic properties of the steel sheets be achieved, but the material waste can also be significantly reduced. This method can be used to manufacture soft magnetic cores from both grain-oriented and non-oriented electrical steel sheets to obtain the highest efficiency using currently available electrical steel sheets. The material waste can be reduced by 50% or more.

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  • ABOUT THE ENTRANT

  • Name:
    Youliang He
  • Type of entry:
    team
    Team members:
    • Damir Sebesta
    • Maciej Podlesny
  • Patent status:
    pending