On the axial and eddy currents induced in a cylindrical core of lossy material heated by an induction coil

When an induction coil surrounds a lossy core so that there is a gap between coil and core, heating of the core takes place by both axial currents and circumferential eddy currents. An equivalent circuit supported by experimental evidence has been devised for this induction coil — lossy core configuration which represents the distributed nature of the coupling mechanism between the coil and the core by simple lumped elements. While induction heating has traditionally been represented by lumped equivalent circuits, such circuits do not account for axial currents which are invariably the dominant source of heating in cores of low conductivity. The proposed equivalent circuit predicts the relative magnitudes of both axial and eddy current heating for virtually any core conductivity.