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Seok Beom Kim,Kaneko, T.,Kajikawa, H.,Jin Hong Joo,Jeong-Min Jo,Young-Jae Han,Hyun-Seung Jeong IEEE 2013 IEEE transactions on applied superconductivity Vol.23 No.3
<P>In the case of motors and generators, the benefits of using high-temperature superconducting (HTS) coils could be represented by the reduction of 50% in both losses and sizes compared to the conventional machines of the same rating. However, it is hard to establish the quench detection and protection devices for the HTS coils applied to the rotors of motors and generators. Therefore, the stability of the coils is lower than the quiescent coils applied to NMR, MRI, and so on. Therefore, it is important to improve the self-protection ability of HTS coils. We have been developing a novel self-protection method, which removes the insulation turn-turn winding and inserts various metal tapes instead of the insulation. In our previous research, the higher self-protection ability for the thermal disturbances in the HTS coils removed the insulation and inserted Cu tape has been proved. This paper presents the results of an experimental study for the quench current using the insulated, the noninsulated, and the Brass tape inserted HTS coils in liquid nitrogen and background magnetic fields. Also, the measured quench currents of each coil will be discussed.</P>
Kim, S.B.,Kaneko, T.,Saito, A.,Kajikawa, H.,Joo, J.H.,Jo, J.M.,Han, Y.J.,Jeong, H.S. North-Holland 2013 Physica. C, Superconductivity Vol.484 No.-
The high temperature superconducting (HTS) coils have very low normal zone propagation velocity (NZPV) and complicated quench behaviors. Because of these reasons, it is difficult to expect the self-protection. In this paper, two methods are suggested to improve the self-protection ability of HTS coils. One is to remove the insulation between turn-turn winding in HTS coils to enhance the thermal and electrical contacts along transverse direction and to increase the whole thermal stability of them. The other is Cu or Brass tapes are wound with HTS tape wire instead of the insulation to improve the thermal, electrical and mechanical stability of the HTS coils. To clarify the quench behaviors of the suggested coils, the normal zone propagation properties of the fabricated non-insulated HTS pancake coils were shown by measured voltage and temperature traces during the quench as a function of the operating temperature. And the characteristics of the normal transition and amount of the shared current to adjacent layers were quantitatively measured by a Hall sensor located at the center of HTS coils to measure the change of the self-magnetic field by operating current. The current sharing behaviors in the non-insulated HTS coil and the coil with Cu tape inserted were observed. The minimum quench energy (MQE) of the HTS coil with Cu tape inserted was the largest in the tested coils. It means that the HTS coil with Cu tape inserted had the highest transient stability against the thermal disturbances among the tested coils and the improvement of self protection abilities was proved.