In the present work, one near‐eutectic and three hypoeutectic Sn‐Ag‐Cu alloys have been employed for soldering by induction heating. The alloys were produced by induction melting of high purity Ag, Cu, and Sn lumps. The melting behavior of the alloys was investigated by differential scanning calorimetry. The solder alloys were subsequently applied for soldering by conventional hot‐plate heating as well as induction heating and both soldering times and peak temperatures were recorded during soldering. Solder joints of two copper sheets were produced. The electrical resistance, tensile strength, and microstructure were analyzed on each soldered joint. The results indicate that the physical and mechanical properties of solder joints are determined by their chemical composition and soldering technology. Induction soldered joints not only have a slightly higher electrical resistivity but also higher mechanical strength, except of the 0.3 wt.% Ag hypoeutectic solder. The highest increase in ultimate tensile strength (28%) was observed for induction soldered joints with 1 wt.% Ag hypoeutectic solder. This effect is ascribed to the homogenous distribution of the intermetallic compounds within the eutectic in the alloy microstructure. The homogenous distribution is aided by rotation of liquid solder due to eddy currents and high‐frequency magnetic field generated during induction heating.

Alternating current (AC) losses in superconducting tapes (SCTs) are one of the main concerns for their use in applications where costs of heat dissipation need to be reduced, such as pulse magnets. Modification of the tapes by striation has been shown to significantly reduce AC losses, and several filamentization methods have been developed. Up to two orders of magnitude decrease in AC losses was reported in previous works with laser ablation, mechanical grooving, or chemical etching. However, a different approach may have to be used to achieve similar results for those SCTs (or their applications after striation), which are more prone to degradation by the side effects of the mentioned methods. We proposed a procedure based on chemo-mechanical etching, which avoids problems arising from thermal degradation and mechanical pressure. Our method intended for the REBCO (RE = rare earth metal, B = Ba, C = Cu, O = oxygen) based high-temperature SCTs yielded low and reproducible AC losses, low cost, retention of the relative critical current up to 93%, and preservation of the mechanical properties of the tape substrate.

A new cabling machine was constructed for conductor on round core (CORC)-like cable production. Its design allowed us to produce a cable with two layers in one run, each comprising four superconducting tapes. The cable of length of 40 m was made at a production rate of 6 m h ⁻¹ by this machine. It consisted of eight Furukawa-SuperPower tapes of width 4 mm and length 50 m wound in two layers on Cu tube with outer diameter 6.35 mm. To detect the influence of the cable winding technology on the superconducting tapes’ properties their critical currents were measured individually on the as-produced cable in the form of a one-layer coil. Afterwards the critical current of the one-layer coil was measured by monitoring the voltages on all tapes while increasing the coil current. The average of these voltages was utilized for coil critical current determination. Then the solenoid with four layers each containing 20 turns was created from the cable and the same measurement procedure was performed to check the influence of cable bending on the solenoid form. The results of these characterizations exclude critical current degradation for any tape of the cable used for solenoid preparation. The measured solenoid critical current of 622.8 A is lower than the simple sum 1240 A of the individual tapes’ critical currents due to the dependence of the tape critical current on the magnetic field. For all measurements the investigated object was immersed into a liquid nitrogen bath. In the case of the solenoid the bath was also cooled down to 66 K.

High-temperature superconducting coated conductors (CC) are attractive materials for high-voltage resistive fault current limiters. Commercially produced CC tapes cannot withstand electric fields over 100 V m⁻¹, and therefore, they have to be modified by addition of thermal stabilization layer. We investigated several composite systems suitable for such thermal stabilization. As a matrix of composites, Stycast resins were used, which contain various contents of powder particles from SiC, SiO₂, PbTiO₃, ZrW₂O₈, or synthetic diamond. The thermo-physical properties such as thermal expansion, heat capacity, thermal diffusivity and direct-current electrical conductivity were measured because they are influenced by filler content in the composite. The possible highest amount of the powder can slightly increase the thermal conductivity and decrease the thermal expansion of the system to an acceptable value needed for the coating of CCs. A side effect is simultaneous drop of heat capacity; however, its value stays still high enough for the purpose of heat sinking. Overall, the best results were achieved in system with 20 vol% of SiC filler in Stycast 2850FT + Catalyst 23LV resin matrix. There the contribution of the semiconducting SiC addition to the electrical conductivity of composite was negligible.

This study aimed to enhance the performance of Ag-stabilized high-temperature superconducting (HTS) tapes with a focus on reducing magnetization losses. Two approaches were employed: dividing the tapes into narrower widths and introducing striation at the level of the superconducting layer. The process of laser ablation proved to be an effective method for implementing these modifications. The quality of the cut edges and grooves was assessed using scanning electron microscopy. To evaluate the electrical properties, measurements were conducted on the critical current and magnetization loss in samples at different stages: in their initial state, after cutting, and after the striation process. Of the two modifications, the striation process more effectively reduced the AC losses in the HTS tapes, approximately by one order of magnitude. The retention of critical current remained high after cutting, but varied with the number of created filaments after the striation process. Subsequently, a short cable was wound from the cut and striated HTS tape. This cable demonstrated a remarkable sixfold reduction in AC losses compared to the initial HTS tape.

We enhanced the performance of superconducting tapes during quenching by coating the tapes with various composites, with regards to the application of such coated systems in superconducting fault current limiters. In composition of the coating, we varied the type of epoxy matrix, the content of ceramic filler particles and the use of reinforcement in order to optimize the thermal and the mechanical stability of the coated tapes. By this way modified superconducting tapes were able to reduce the maximum temperature 170 °C of not modified superconducting tape to 55 °C during the quench with electric field up to 130 V m⁻¹.