Eddy currents in solid iron due to alternating magnetic flux

The predetermination of the phenomena connected with the penetration of alternating flux into solid iron due to an alternating magnetic field is a problem of great complexity. The prediction is particularly difficult in the presence of saturation. The object of the paper is to present a unique graphical construction which would enable the designer to compute readily quantities such as flux, eddy-current loss, etc. This single construction has the merit of suitability for determining the above quantities for any magnetic material over any desired range of frequencies. A close examination of the geometry of the graphical construction leads to a new method of formulating the basic equations. This method of approach brings out the importance of the law of variation of the magnetizing force with the depth of penetration of the flux for the determination of all other relevant quantities associated with the phenomena. On the basis of the basic differential equations, a law for the field intensity is suggested, to take saturation into account. This law is shown to agree favourably with the results of the graphical construction. The analysis is applied to two different magnetic materials and is verified experimentally.