TUM: Steel sheets decisive for efficiency of electric motors


Researchers from the TU Munich (TUM) have optimised the cutting process for steel sheets used in electric motors, thus increasing the drives’ efficiency by keeping the sheets magnetic properties in tact.

Blunt force used in the production of electric steel sheets for electric motors is a problem, a team at TU Munich has found.

The scientists have investigated the way these steel sheets are processed and have concluded that using blunt cutting tools deteriorates the magnetic properties of the steel sheets significantly. In turn, this also decreases the efficiency of the electric motors since these sheets generate the magnetic fields that move the motor using attractive and repulsive forces.

In their workshop, the researchers from the TUM Chair of Metal Forming and Casting have looked at how these sheets are cut and stamped in detail. Together they found that the sharpness of the cutting tools used has a significant impact on the magnetic properties of the steel sheets.

The effect can be compared to a pair of scissors which dulls over time, worn cutting edges result in higher tension in the steel sheets themselves – the material is bent and thus subject to increased mechanical stress, that then has a major impact on magnetic properties. “In some cases as much as four times the amount of electricity is needed to achieve the same degree of magnetization,” explains project director Hannes Weiss.

Weiss and his team have formulated recommendations for the production process. However, economic factors also have to be taken into account, the engineer explains: “When the cutting tools and their maintenance incur additional costs, the final price of the electric drives produced rises as well.”

Project work was conducted under the first part of the research project FOR1897 on low-loss electrical steel sheets for energy-efficient drives, with the support of the German Research Foundation (Deutsche Forschungsgemeinschaft or DFG).



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