Improved Transformer Noise Behavior by Optimized Laser Domain Refinement at ThyssenKrupp Electrical Steel

The present paper shows the impact of different laser domain refinement variants for grain oriented electrical steel on the noise of three-phase transformer cores. The impact is evaluated as well by calculated noise on basis of magnetostriction measurements of the electrical steel sheets as by measured noise of transformer core models built from these GO electrical steel sheets. The industrially relevant process of laser domain refinement is reviewed with respect to the influence of different process parameters on the later materials and transformer performance. Contrary to the usually admitted statement, it is demonstrated, that (a) the use of optimum laser domain refinement conditions will not increase the noise level of the transformer cores compared to the non DR status and (b) the use of magnetostriction data for judging about later transformer noise is resulting in only rough indications, but not the final behavior of the real cores.