## 3 Experimental Results  
An experiment was performed to verify the simulation results of the proposed quench detection method. The experimental set-up used for the verification is shown in Figure 10.  
As in the simulation, the amplitudes of the EMF and noise signals are the same values in the experiment. This is because the resonance filter results in a reduction in the amplitude of the noise component, as is the case with the simulation results. In addition, a heater trigger using nichrome wire was installed on the outmost turns of INS and NI coil to cause quenching. The heater trigger was turned on after 60 s from the start of the voltage measurement. Table 2 shows the specifications of the superconducting coil parameters and values. Figure 8: Transfer function shape of the resonant circuit using the NI coil. Figure 7: FFT analysis results using the not-insulated (NI) coil. Figure 9: Equivalent circuit to explain the filter characteristics according to the shape of the transfer function: (**a**) INS coil and (**b**) NI coil. Figure 11 shows the experimental results. As shown in Figure 11, the voltage signal measured at both ends of the \(R_{ext}\) in the time domain. Moreover, in Figure 11 and c, are shown the results of the FFT analysis of the experimental results for 0.5 s in the superconducting and normal state, respectively. However, as can be seen in Figure 11, although quenching was generated after 60 s, it was difficult to detect the quench in the time domain. The reason for this is that the HTS does not show a significant increase in resistance compared to an LTS, even though a quench occurs. However, comparing the amplitudes of the EMF signals in Figure 11 and c it is possible to confirm that the quench occurs. Moreover, as confirmed from the simulation results, the amplitude of the noise signal decreased due to the effect of the resonant filter. However, in an industrial environment, noise having various frequencies can be included in the measured signal. These noise components should be reduced in the conventional quench detection method. However, because the method proposed in this paper uses only the amplitude change of the EMF signal corresponding to the resonance frequency, these noise components are not considered. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{2}{c}{**Stator Coil**} & \multicolumn{1}{c}{**Rotor Coil**} \\ \cline{2-4}  & **NI Coil** & **INS Coil** & \\ \hline
**IC (@ 77K, Self) [A]** & \textless{}80 & \textless{}65 & - \\
**Coil Type** & \multicolumn{2}{c}{Single Pancake} & Solenoid \\
**Turns** & \multicolumn{2}{c}{30} & - \\
**I.D. [mm]** & \multicolumn{2}{c}{65} & 100 \\
**O.D. [mm]** & \multicolumn{2}{c}{80} & 83 & 120 \\
**Inductance [mH]** & \multicolumn{2}{c}{0.125} & 0.123 & 11.4 \\
**Time Constant [ms]** & \multicolumn{2}{c}{70} & 400 & - \\
**Insulation Material/Thickness [mm]** & \multicolumn{2}{c}{-} & \multicolumn{2}{c}{Kapton/0.05} \\ \hline
**Type** & \multicolumn{2}{c}{SuNAM 2G HTS Tape} \\
**HTS Tape** & \multicolumn{2}{c}{**Width [mm]**} & 4 & 12 \\
**Thickness [mm]** & \multicolumn{2}{c}{0.25} & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Specifications of superconducting coil parameters and values. Figure 10: Experimental set-up for verification of the simulation results. components are not considered. This is because the amplitude of the noise components is smaller than that of the EMF signal due to the characteristics of the transfer function of the resonance filter. Therefore, only the frequency component corresponding to the EMF signal is measured to detect the quench. Figure 12 shows the results of FFT analysis using a 70 Hz signal corresponding to the resonance frequency of the circuit. As shown in Figure 12, it is possible to distinguish between the superconducting state and the normal state based on the 60 s when the heater trigger is turned on, so that the quench can be detected.