Speakers
Description
The high temperature superconductor (HTS) direct current (DC) induction heater shows great advantages on high efficiency and heating quality in comparison to traditional AC induction heater. A commercial megawatt (MW) HTS DC induction heater using REBa2Cu3O7-δ (REBCO) conductors has been developed by Shanghai Jiao Tong University and JIANGXI Lianchuang Opto-eletronic Science and Technology Company Ltd., China. The heater is to preheat aluminum billets with a diameter of 446 mm and a length 800–1500 mm. The HTS magnet are wound by 18 km REBCO tapes from Shanghai Superconductor Technology Company. The HTS coils are coupled with an iron core to generate 0.5 T DC magnetic field at air gaps where aluminium billets are rotated by motors.
The development of this commercial 1-MW HTS DC induction heater has suffered three main technical challenges, which will also occurs widely on the other commercial HTS DC induction heaters. First, the inductance of the HTS magnet with iron is about 100 H, which is challenging for the quench protection of HTS coils. We have tried to apply the no-insulation coil technique to enhance the thermal stability, however, this leads to another problem of ramping delay. Based on optimization analysis, comprehensive multiple measures are developed to ensure the thermal safety this HTS magnet. The second technical challenge is how to drive the billet economically. A peak electromagnetic torque is generated during the start-up of the aluminium billets, which is more than 3 time of the operating torque. The third technical challenge is how to achieve the control of temperature gradient along the axial direction. An adjustable temperature gradient (up to 100 °C) along axial direction is achieved by adjusting the axial field distribution, which is a novel and unique feature of this heater design. The technical experiences of this project are valuable and useful for the commercial HTS DC induction heater and other industrial HTS applications.
