A simple method to estimate the magnetic field distribution due to current-carrying winding in toroidal core and its influence on the measurement of complex permeability and core losses

When we measure the power losses and the complex permeability mu = mu'(r) - j mu "(i) of magnetic core, several turns of winding are wound tightly aro und the toroidal core to be measured. In order to make the magnetic field p roduced by the winding current in the core more uniform around the core, mo re turns of winding are needed. In this paper the distribution of the magne tic field strength produced by the winding current is analyzed based on the Biot-Savart law. According to the calculated result, we found the external field strength is much bigger in the area covered by the winding than the area unsurrounded by the winding. In order to study the influence of the no nuniform distribution of the external field strength on the measurement of the complex permeability and core loss, we use two sets of coils with the s ame turns connected in parallel which are arranged symmetrically around the core. From the measured results, it is found that core loss is not influen ced by the distribution of the external magnetic field strength but the com plex permeability is affected by the arrangement of the winding along the t oroidal core. (C) 1999 Published by Elsevier Science B.V. All rights reserv ed.