Induction Heating of Aluminum Billets Subjected to a Strong Rotating Magnetic Field Produced by Superconducting Windings

This paper presents an analysis of an original structure of induction heater using superconducting coils. With the proposed structure, two operating modes are possible to heat the aluminum billet. Either the billet is at standstill and placed within a strong rotating magnetic field (around 3.5 T) of low frequency (around 1 Hz), or the billet rotates at low angular speed (around 6 rad/s) within a strong dc magnetic field (around 3.5 T). The analysis is based on the analytical solution of two-dimensional diffusion equations for the magnetic vector potential. A closed-form expression is derived for the eddy-current power loss in the billet. This analytical expression can be used as a tool for design optimization of the induction heater. The analytical results are compared with those obtained by finite-element software. The study of the temperature field in the billet shows that a homogeneous temperature profile is obtained when a strong magnetic field of low frequency (rotating speed or ac current pulsation) is used.