Coupled Analysis and Protection of the HTS DC Magnet for DC Induction Heater in Dynamic Disturbance

Designing a high temperature superconducting (HTS) DC induction heater requires the HTS magnet to be equipped with an HTS coil, iron core and air gap. A large amount of magnetic energy is stored in the iron core and must be transferred outside the magnet during system collapses. The nature of the operating conditions and dynamic heating processes make the magnet coil a substantial nonlinear inductive load for the power supply which can result in system collapse and potentially damage the peripheral circuit of the magnet. Therefore, a protection system is recommended for this magnet. This paper proposes an active protection system for a DC HTS induction heater composed of a magnet with an iron core and YBCO coated conductor (CC) tape. A Matlab/Simulink-based simulation model was coupled with a Comsol-based finite element method model to combine the electrical and electromagnetic characteristics to optimize the design configuration of the protection circuit. Experiments with different magnet operating currents and dump resistors were carried out to verify the feasibility of this proposed protection system for magnets with and without an iron core. The results show that the proposed scheme performs within desired specifications and that the dissipation efficiency and velocity vary depending upon different values of the dump resistor.