Research on ZnO Varistor for Superconducting Magnet Quench Protection

Quench protection is a major subject for superconducting magnets, which operate at high current densities with high stored energy. Large amounts of energy should be removed to protect magnets. Due to its nonlinear properties, the zinc oxide (ZnO) varistor shows strong advantages compared to the constant resistance. In this work, the characteristics and its superiority over the constant resistance are demonstrated. First, the changes of current and voltage are analyzed during the discharge process. We find that the discharge time are shortened and the efficiency are increased in case of ZnO. Second, we report the experimental setup, including the rare earth (RE) Ba₂Cu₃O₇-x (REBCO) magnet, energy transfer elements, and the corresponding test platform. The experimental results show that the constant voltage demagnetization can be realized. This is consistent with the presented theoretical analysis.