Calculation of the Self-inductance of a Rectangular Magnetizer Coil

The self-inductance of the operating coil of a magnetizing device is calculated using different methods. The winding of the coil under investigation basically consists of copper sheets with rectangular concentric inner and outer contours. These plates form the turns of a Bitter coil. They are stacked together with an electric insulation between them and connected in series to form a helix-like winding. Analytical formulae for cylindrical coils can only be applied as a coarse approximation due to the rectangular cross-section and because of exact geometric measures of current paths such as for arrangements of filamentary wires not being available. More reliable results are obtained, if first self- and mutual inductances of all turns are determined according to Neumann’s formula and the resulting self-inductance is determined afterwards with respect to the connection for all turns in series. A 3D-FEM analysis is carried out in order to verify the method described above and to judge the influence of eddy-current phenomena, i.e. the skin-effect, which might become important in the usual transient operation mode.