Measurement of the Electric Properties of the KSTAR CS Model Coil

Chu

et al. 2011

Windings of Nb 3 Sn cable-in-conduit conductors of the toroidal field (TF) and the 1st-5th poloidal field (PF) coils of the Korea Superconducting Tokamak Advanced Research (KSTAR) have Incoloy-908 jackets, which exhibit weak ferromagnetism. The inductance of the PF coils was measured by monitoring the induced voltages on the coils while TF coils were steadily energized at 20 kA, and one of each pair of PF coils was charged up to 4 kA at 2 kA/s. At a large PF current, the measured self inductance was very close to the design value. In contrast, the measured self inductances of the PF1-PF5 coils increased 90-135% by decreasing their current below 2 kA; whereas those of the PF6-PF7 coils almost stayed at the same levels. On the other hand, the measured self inductances were much smaller than the other measurements obtained at no TF current. The self induced voltage was almost cancelled out by using a single Wheatstone bridge of the quench detectors; whereas, the mutually induced voltage was cancelled out by numerically subtracting outputs of two Wheatstone bridges for coils, which were symmetrically located in the assembled coils.Index Terms-Incoloy 908, inductance measurement, KSTAR, quench detection.

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Section: A Inductancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Experimental Evaluation of Inductance and Its Impact on Quench Detection of the KSTAR Coils

Chu

et al. 2011

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“…On the other hand, Incoloy 908 has a low relative permeability of 8 to 12 and also saturates in a low external magnetic field around 1.3 kG [4]. Because of its low magnetic permeability, the magnetic properties of Incoloy 908 are often dismissed in the calculation of magnetic fields; however, in a test of the KSTAR CS model coil made of the CICC, its self inductance increased up to 80% at a small current below 200 A due to the permeability of Incoloy 908 [5]. Thus, the assembled KSTAR coils may generate a magnetic field with some discrepancy between measurements and calculated values under the assumption that there is no magnetic influence of Incoloy 908.…”

Section: Introductionmentioning

confidence: 99%

KSTAR Magnetic Field Measurement During the Commissioning and Remanent Field Evaluation

Lee

et al. 2009

Self Cite

An in-situ measurement of the magnetic field generated by the assembled superconducting magnet coils was held by using precision Hall sensors during the commissioning of the Korea Superconducting Tokamak Advanced Research (KSTAR) device. This was done in order to investigate the magnetic influence of Incoloy 908, which is the jacket material for the cable-in-conduit conductors (CICCs) of the Nb 3 Sn coils. After the PF coils were discharged from 1 kA the vertical remanent field at the plasma center was more than 10 G, while the TF coils were not energized. The vertical magnetic field generated by the PF coils had a discrepancy of up to 50 G between measurement and the calculation assuming no magnetic influence of Incoloy 908. Thus, non-negligible ferromagnetism was identified and attributed to Incoloy 908. In contrast, most of the hysteresis observed in the magnetic measurements was eliminated when the Incoloy 908 of the TF windings was saturated by the TF coil charging.Index Terms-Incoloy 908, Nb 3 Sn, remanent magnetic field, superconducting magnet coil.

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Quench Detection Based on Voltage Measurement for the KSTAR Superconducting Coils

Chu

et al. 2009