Numerical and experimental analyses of the deterioration in magnetic flux density distribution on perforated transformer core steels

Abstract

AbstractThe holes in transformer core sheets are necessary for tailoring transformer‐core designs even though they cause more or less deterioration in the magnetic properties. With using spark erosion, specimens were pierced as a circle shape at certain locations and diameters to compare their effects to the magnetic properties by means of hysteresis curves, Magneto‐optical Kerr imaging, and finite element method. It was found that piercing the middles and corners of sheets at regular intervals dropped the sheets' relative permeabilities to ranges of 28% to 70%. Additionally, significant increments in power losses, from 0.8 to 2.54 W/kg at 50 Hz, depending on increases in hole diameters, were noted. These effects did not occur in a non‐pierced sample. Furthermore, considering all possible scenarios based on hole diameters and locations, laminated transformer‐core sheets were simulated to study distributions of flux lines, flux densities, and magnetic forces using 2‐dimensional static magnetic analyses. Holes in the sheets and the holes' proximities to each other were noted using magneto‐optical Kerr microscopies. Kerr images and diagrams of flux propagation from the simulation were individually compared to consider how the sheets flux distributions were influenced by varying the physical properties of the holes. The cases' effects on basic transformer cores were also investigated using 2‐dimensional static analyses.