MAGNETOSTRICTION DISTRIBUTION IN A MODEL TRANSFORMER CORE
Georgi Shilyashki – Helmut Pfützner – Franz Hofbauer – Damir Sabic – Viktor Galabov
The primary aim of this work is to study the distribution of magnetostriction-caused strain in different regions of a model transformer core. A technique of measuring the peak-to-peak strain ε with a high number of well averaging strain-gauges is presented. The results indicate very high variations of ε. In rolling direction, limbs and yokes show values of ε below 1 ppm, close to catalogue values of magnetostriction (MS). Corners exhibit values up to 2.5 ppm, probably with strong contributions of magnetostatic forces. T-joints show values up to 3 ppm due to high MS as being typical for rotational magnetization apart from contributions from forces. Generally, much lower values were found for the transverse direction. As a main conclusion, a major contribution for vibrations can be expected for the axial direction of yokes.
Keywords: magnetostriction, core vibration, transformer noise, magnetostatic forces