Quench Detection Method for HTS Machines by Differencing Terminal Voltage of HTS Coils in Symmetrical Positions

High-temperature-superconducting (HTS) coils have been attracting more and more attention in electrical machines as excitation coils due to its zero-resistance characteristic. However, the quench of HTS-excitation coil will seriously threat the safe operation of electrical machines. At present, the voltage detection method is mostly applied to detect the quench of HTS coils. However, the traditional voltage detection method cannot eliminate the influence of induced voltage coupled in terminal voltage of HTS-excitation coils, thus commonly causing quench misjudgment. Therefore, a quench detection method for structure symmetric HTS electrical machines is developed in this paper. The key of the proposed method is to eliminate the induced voltage by calculating the difference between the terminal voltages of HTS-excitation coils in symmetrical positions, thus significantly enhancing the accuracy of the quench voltage detection. By using the finite element analysis (FEA) applying the proposed method in a double-stator HTS machine (DS-HTSM), its validation is verified.