AC loss performance of the 100 kWh SMES model coil

Hamajima, T.; Hanai, S.; Wachi, Y.; Kyoto, M.; Shimada, M.; Ono, M.; Shimada, Kazuhiko; Kushida, L.; Tezuka, M.; Martovetsky, N.; Zbasnik, J.; Moller, J.M.; Takahashi, Yoshikazu; Matsui, K.; Isono, T.; Yamamoto, Masahiro; Takano, Ichiro; Himeno, Takashi; Hirano, Naoki; Shinoda, Kimiyuki; Satow, T.

doi:10.1109/77.828355

Cited by 14 publications

(11 citation statements)

References 13 publications

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“…The signals revealed the long time constants of about 4 s and 100 s occurred in the coil, while other signals from other probes indicated various time constants from 4 s to 110 s [2]-[4]. It was also confirmed from flux loop decay signals of voltage taps soldered on the conductor that the loop time constant was about 130 s[3]. Consequently, there existed various long time constants in the SMES model coil, and hence the averaged long time constant was about 30 s. If current rise time is the same order as the averaged long time constant, the irregular losses become larger than the regular coupling losses.…”

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confidence: 82%

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Long time constants of irregular AC coupling losses in a large superconducting coil

Hamajima

Harada

Satow

et al. 2002

IEEE Trans. Appl. Supercond.

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A large superconducting coil wound with Cable-inConduit (CIC) conductor caused an irregular AC loss that cannot be estimated from short conductor sample test results. It was confirmed that the irregular AC loss was generated by long current loops in the CIC conductor. We proposed a mechanism forming the long loops. The CIC conductor is composed of several staged sub-cables. If one strand on the surface of a sub-cable contacts with the other strand on the surface of the adjacent sub-cable, the two strands must encounter each other again at LCM (Least Common Multiplier) distance of all staged cable pitches and thereby result in forming a pair of a long loop. We measured cross over point contact resistance between two strands making the long loop. The calculated time constants of the long loops were shorter than the observed ones. We orderly labeled all strands in a real CIC conductor, disassembling carefully the cable after peeling the conduit. It was found that the strands in a triplet were widely displaced from their original positions, and thereby their contacting lengths became longer than cross over ones to form line contacts. This fact can make the time constant of the loop longer and hence can explain the observed long time constants.

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confidence: 82%

“…The AC losses in the SMES model coil were measured for various rise times and peak currents [1]- [3]. Their normalized AC losses are shown in Fig.…”

Section: A Measured Coupling Lossesmentioning

confidence: 99%

Long time constants of irregular AC coupling losses in a large superconducting coil

Hamajima

Harada

Satow

et al. 2002

IEEE Trans. Appl. Supercond.

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“…These resistances are not so small corresponding to time constants for the SMES and LHD-IV conductors of less than and 0.3 s, respectively. Because the cross over contact is a point less than 0.1 mm in length, this observation lead us to in- On the other hand, we have also measured the cross-over contact resistance of CuNi coated strands used for the improved SMES coil (Table II), where the irregular AC losses were not observed [2], [3]. The resistance was about 1 m that is about 20 times as large as those of strands in the SMES and LHD-IV conductor.…”

Section: Contacting Resistances Of the Loopsmentioning

confidence: 96%

“…[3]. Clearly, there existed loops with long time constants, and we estimated the averaged to be about 30 s. If current rise time is the same order as the averaged long time constant, the irregular losses may become larger than the regular coupling losses.…”

Section: Irregular Coupling Ac Lossesmentioning

confidence: 99%

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Irregular AC losses with long time constants in large cable-in-conduit conductors

Hamajima

Kakusho

Hoashi

et al. 2003

IEEE Trans. Appl. Supercond.

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A large superconducting coil wound with Cable-in-Conduit (CIC) conductor causes both irregular AC losses that cannot be estimated from short conductor sample test results, and regular AC losses that are proportional to cable twisting pitch squared. We proposed a mechanism forming loops that generated the irregular losses. The CIC conductor is composed of several stages of sub-cables. If one strand on the surface of a sub-cable contacts another strand on the surface of the adjacent sub-cable, the two strands must encounter each other again at the LCM (Least Common Multiplier) distance of all staged cable pitches, and thereby a long loop is formed. We orderly labeled all strands in CIC conductors for the SMES and the LHD. It was found that strands in a triplet were widely displaced from their original positions on one cross section, but contacted each other tightly on the other cross section. This fact suggests that the loop with the large displaced strand links irregularly with external field so that the loops cause the irregular AC losses. Moreover, it indicates that a contacting length of the large displaced strands can be quite long, giving rise to a low contact resistance for the loop, and leading to the long time constants. It is believed that the widely displaced strand are inherent in a CIC conductor. It was demonstrated that the strand surface coated with CuNi was effective to suppress the irregular AC losses.

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Hysteresis and Coupling Losses in Superconductors

Bruzzone

1999

Wiley Encyclopedia of Electrical and Electronics Engineering

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AC loss performance of the 100 kWh SMES model coil

Cited by 14 publications

References 13 publications

Long time constants of irregular AC coupling losses in a large superconducting coil

Long time constants of irregular AC coupling losses in a large superconducting coil

Irregular AC losses with long time constants in large cable-in-conduit conductors

Hysteresis and Coupling Losses in Superconductors

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