Helmut Pregartner

Experimental determination of specific power losses and magnetostriction of electrical steel coils

A method for measuring the specific losses and magnetostriction of grain-oriented electrical steel coils up to six tons is presented. Since transformer core manufacturers are mainly supplied with entire steel coils, a fast incoming goods inspection is desirable. The proposed method identifies the specific losses at certain flux densities of the entire steel coils. In addition, the magnetostriction of the coiled material is measured. With the magnetostriction the main property for transformer no-load noise can be classified. The structure and setup of the developed coil measurement system (CMS) are shown. The measurement technique is explained and its requirements are identified. Initial results of specific power losses and magnetostriction of electrical steel coils as well as the reproducibility of the results are highlighted.

Magnetic properties and their relation to the no-load noise and no-load losses of large power transformers

The performance of the no-load losses and core noise of large power transformers (LPT) can be attributed to the magnetic properties of the deployed grain-oriented electrical steel (GOES) material. Measurements of different GOES materials have led to findings about their performance. Four LPT cores, each with a mass of 40 metric tons, were manufactured out of 187 GOES coils with the same material grade but with different properties. Before the transformer cores were manufactured, each of the deployed GOES coils was measured with an in-house coil measurement system (CMS) to obtain the specific power losses and the magnetostriction. This paper shows a first comparison between the measured GOES coils magnetic properties and LPTs. First, the measured magnetostriction of the GOES coils and their predictability on core noise of the LPTs are evaluated. In addition, the assessment of the GOES coils specific power losses and the no-load losses of the LPT units are shown.