Progress in Superconductivity and Cryogenics (한국초전도ㆍ저온공학회논문지)

The Korean Society of Superconductivity and Cryogenics (한국초전도저온학회)
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Analysis of AC losses in HTS coils by temperature variations

  • Received : 2017.08.03
  • Accepted : 2018.12.18
  • Published : 2018.12.31
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Abstract

We analyzed the temperature dependency of the AC losses in high temperature superconducting (HTS) coils. In the case of a short sample of an HTS tape, the magnetization loss at 4.2 K could be higher than the one at 77 K for a same transport current. It happens when the perpendicular magnetic field is above a certain magnitude. The AC loss characteristics of solenoidal coils have been analyzed at the temperatures of 65 K and 77 K. They were categorized by the aspect ratios. The operating current of a solenoid was normally set about 70 % of the critical current. An HTS solenoid with the same operating current of 77 K causes larger AC losses at 65 K in the most cases of the HTS solenoids. We also analyzed the AC loss characteristics due to the temperature variations for three types of superconducting magnetic energy storages. Two of them were solenoidal types and the other was toroidal type. The results showed the tendency for the coils to have higher AC losses at lower temperature with the same operating currents and scenarios.

Keywords

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Fig. 3. The normalized loss (loss@65 K to loss@77 K) according to (α, β) for a1= 50 [mm]. Most solenoids except very thin ones have larger AC losses at 65 K when the operating AC currents are same at both temperatures, (a) 1.01 <α< 5, (b) 1.01 <α< 1.1.

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Fig. 5. Bird’s eye views of three SMESs. (a) 600 kJ solenoidal type, (b) 2.5 MJ toroidal type, (c) 5 MJ solenoidal type.

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Fig. 1. Calculated magnetization losses of an HTS tape by magnetic flux densities of at 4.2 K and 77 K.

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Fig. 2. Definition of HTS coil shape. The ratio of α=a2/a1, β=b1/a1.

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Fig. 4. B-I curves of the 4 mm width HTS tape.

TABLE I THE OPERATING TEMPERATURE RANGES OF HTS APPLICATIONS.

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TABLE II SPECIFICATION OF 2G HTS TAPE FOR THE ANALYSIS.

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TABLE III SPECIFICATIONS OF THREE SMESS.

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Fig.6. Operating scenarios of SMES. Scenario 1 is full discharging condition and scenario 2 is repetition of charging and discharging.

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TABLE IV. THE CALCULATED AC LOSSES OF THREE SMESS.

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