Comparative Analysis of Loss Characteristics in DCCTs at Cryogenic Temperature With HTS and Copper Compensation Windings

Accurate condition monitoring of high-temperature superconducting (HTS) cables in ultra-high-field magnets requires precise current measurement at cryogenic temperatures. Direct-Current Current Transformer (DCCT), a current measuring device based on zero-flux principle, is widely used as a high-precision measurement scheme. However, commercial DCCTs employing copper compensation coils exhibit significant operational losses at high currents, limiting their performance and range in low-temperature environments. To overcome this limitation, this paper proposes a conceptual design of an HTS compensated DCCT, an innovative approach to cryogenic current sensing. A comparative analysis of the loss characteristics between conventional copper and the proposed HTS compensation coil is conducted through finite element method (FEM) simulations. The results demonstrate that the copper coil generates losses 103to 105times greater than the HTS coil under high-current conditions. Consequently, the HTS compensated DCCT achieves a superior current range of up to 70 kA at 20 K, with virtually no steady-state loss and significantly reduced ramping loss. These findings confirm that the minimal loss characteristics of the HTS winding establish a promising solution for high-precision, high-current measurement in cryogenic applications.