Experimental impact of pulsed laser irradiation, scribing and ablation on 2-D scalar and vector magnetic losses and general properties of Grain-Oriented Electrical Steels

Abstract

Increasing the efficiency of electrical equipment and machines (transformers, large alternators) is a global aim and a way to contribute to its fulfilment is to reduce iron losses of soft magnetic materials within their magnetic cores. Improvement of soft magnetic material properties, especially Grain-Oriented Electrical Steels (GOES), is possible using surface laser treatments and is classically obtained for alternating fields parallel to the Rolling Direction (RD). However, flux lines are not always parallel to this preferred direction and can also rotate. The behavior of laser treated GOES under rotational and alternating fields parallel to the Transverse Direction (TD) remains slightly explored and can be investigated further. In this paper, the magnetic behavior of GOES samples is measured with both unidirectional (with Single Sheet Tester (SST)) and rotational (with Rotational power loss Single Sheet Tester (RSST)) fields. Then, the experimental impacts of different laser treatments (irradiation, scribing and new laser process called ablation with Ultra-Short laser Pulses) on 1-D, 2-D and rotational magnetic losses are compared and discussed. The goal is to optimize the vector behavior of GOES. Power loss reductions are reported for several laser sets of parameters and for several polarization/frequency conditions under both unidirectional and rotational fields. Finally, a short analysis on the difference between rotational and average alternating losses leads to use 2-D vector magnetic properties involving a RD-TD coupled loss contribution while characterizing soft magnetic materials.