Optimised laser processing leads to improved transformers

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Fraunhofer Institute for Material and Beam Technology (IWS), Dresden, Germany, has both advanced the processing of electrical steel, and improved its performance by using a galvanometer scanner and fibre laser to manufacture parts.

Electrical steel is an iron-silicon alloy used for making the cores for the transformers. Transformers are found in nearly every electrical device and are commonly used to take the standard voltage from a wall socket and reduce it to the lower voltages required.

Lasers are used in heat treatment of electrical steel which alters the material's magnetic properties and reduces energy lost during the voltage conversion. Dr Andreas Wetzig, head of the laser ablation and cutting department, Fraunhofer IWS, explained that the laser applies heat along certain paths which changes the crystalline structure within the region. This reduces the size of domains with the same magnetic orientation, which lowers heat development and in turn energy lost through hysteresis.

Fraunhofer IWS has optimised the process of creating these paths by deflecting the laser beam with a galvanometer scanner. This allowed the researchers to adapt to specific conditions including the quality of the raw material and required production rates.

The team also recently started using solid-state fibre lasers instead of CO2. Wetzig said that fibre lasers offer better heat absorption characteristics than the more traditional CO2 and that the results obtained so far have been very promising. This helped cut hysteresis loss by up to 15 per cent compared to typical reductions of 10 per cent.

This new process is already being implemented by one commercial customer; however, the research team is already working on the next stage to expand the applications of its technology and make it possible to use this technique to process electrical steel for engine components. The team believe the results could yield cuts in energy loss of up to 25 per cent in high-torque electric motors. However, unlike transformer steel, this creates new challenges for the team as the materials used here do not have a grain-oriented structure and therefore possess different magnetic properties.

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