A Dynamic Self-Coupling Fast Discharge Method for High Temperature Superconducting Magnets

Fast discharge is important for quench protection of insulated high temperature superconducting (HTS) magnets. Using the dynamic electromagnetic coupling with secondary coils is an effective method to accelerate the discharge process of HTS coils. In an HTS multiple coil system, coils located at low perpendicular field positions have large current-carrying margins, which can be used to store a portion of the energy in the quenched coil. In this article, a self-coupling discharge method for multiple-coil insulated HTS magnets is proposed, and a protection system is designed for a seven-coil 12 T HTS magnet. According to the position of the quenched coil, dump resistors with different resistances are placed to each discharge circuit. Based on self-coupling, a portion of energy stored in the quenched coil is transferred to nonquenched coils. A numerical simulation model is established to verify the effectiveness of the self-coupling discharge method. The results show that this method effectively accelerates the discharge speed of the quenched coil, and the nonquenched coils have sufficient current safety margins. Owing to the slow change in the magnetic field, the peak voltages of most coils during the discharge process are greatly reduced, which reduces the risk of insulation breakdown. This method provides an approach for quench protection of HTS multiple-coil systems.