SPUTTERED SEARCH COILS FOR FLUX DISTRIBUTION ANALYSES IN LAMINATED MAGNETIC CORES

Localised regions in a transformer core, such as joints, are well know n to have distorted magnetisation waveforms. Earlier, 30-100 mu m thic k search coil wires have been introduced in the joint regions to inves tigate the nature of flux distributions which show high relevance for the core's power losses. This thickness exceeds considerably the typic al interlaminar spacing of some mu m, thus affecting the interesting d istribution of flux. In the present work such artifacts were overcome by means of only 1 mu m thick copper search coils sputtered on laminat ion surfaces. Crucial problems of galvanic contacts between the search coils and the SiFe material were met by 0.25 mu m thick SiO2 depositi ons prior to sputtering. Practical applications were performed on a li nearized model of a transformer joint region. The relevance of results was checked numerically using 2D finite element method. The results s how that the take-over of flux may arise in a locally most concentrate d way, i.e. in sheet end regions of less than 1mm length. Air gap brid ging sheet regions prove to be strongly saturated, with induction valu es up to 2.6 T.