Design and Test Performance of 2G Pancake Coils for HTS DC Induction Heater Prototype

To improve the poor efficiency of the conventional induction heater using copper coil, a high temperature superconducting (HTS) DC induction heater is considered. In this study, we designed and built an HTS DC induction heater prototype with an iron core, and tested the insulated and no-insulation (NI) double pancake coils (DPCs). The results show that the critical currents of the DPCs with the iron core somewhat decrease than those without the iron core. The V-I curve of the insulated coil is a standard one of the superconductor, but a linear voltage appears in the NI coil due to the contact resistance between neighboring wires. For the insulated coil, the magnetic flux density of the air core is proportional to the coil current. However, a charging delay is found in the NI coil: The increment of the magnetic flux density for the NI coil is negligible when the current is increasing at first. Then the magnetic flux density increases and finally saturates even if the current is stable. The inductance of the coil with the iron core is about six times of that without the iron core.