Self-field Loss in AC Transport Current Loss of MgB2 Superconducting Composites

The self-field loss on AC transport current for in situ PIT processed MgB2 superconducting tapes with carbides addition and the carbon steel sheath

“…J c decreased as temperature raised, 136 A/mm 2 at 20 K and 110 A/mm 2 at 25 K and 75.9 A/mm 2 at 30 K for no-added wire. J c of the wire with SiC addition was 110 A/mm 2 at 20 K and 89.7 A/mm 2 at 25 K and 58.6 A/mm 2 at 30 K. These values are one order of magnitude higher than those of the previous wires with CuNi sheath and Ni sheath [1,2].…”

“…A conventional four-terminal method is used for adjusting the phase in AC loss measurement [1,2]. In this method, inductive voltages and electromagnetic noises superposed on the terminal voltage of the superconductor were eliminated by using a cancel coil and a lock-in amplifier, and then very small resistive voltage can be precisely measured.…”

“…The sample wire connected with spiral loop voltage taps was mounted on the sample holder made of AlN, and current leads were placed in the cooled region [1,2]. Thermometers of Cernox were attached on the sample wire and on the sample holder.…”

“…As reduction of the AC loss is one of the most important issues for the AC application, its estimation and clarification of causes that influence it are essential. For those demands we studied the transport current loss (self-field loss) against temperature, frequency and AC transport current for the ex situ PIT MgB 2 wire with the metallic sheath materials of CuNi, the stainless steel, and Ni filled with the MgB 2 powders and additional powders, In and Sn [1,2]. The results showed that the inhomogeneity of the MgB 2 core affected the losses.…”

Dependence of Transport-Current Losses in ${\rm MgB}_{2}$ Superconducting Wire on Temperature and Frequency

“…Since both the MgB 2 superconducting windings for rotor and stator in the motor are located inside iron cores, the windings are scarcely exposed to the external magnetic field, and therefore the self-fields due to currents flowing in the windings themselves become dominant. The threephase alternating currents are supplied to the stator winding in the proposed motor to generate a rotating magnetic field inside, so that a detailed understanding of AC loss properties in the MgB 2 windings is one of the key factors to realize the cryogenic superconducting pump although the AC loss measurements of various kinds of MgB 2 wires have been carried out so far [13]- [15].…”