The flux motion and its collective behaviour known as AC loss is the basic characteristic of high temperature superconducting (HTS) materials and controls the economic efficiency, stability and magnetic field uniformity of superconducting equipment. In so far, we have no method to calculate the AC loss of HTS devices in an efficient way. Normally, it will take days to simulate AC loss of HTS coils even with moderate number of turns. In this paper, we surprisingly found that an integral method is remarkably efficient in calculating AC loss of the coils in large scale. By comparing with the fastest method at present, the integral method is proved to be 4.4 times faster than the present one. We give the calculation details and discuss why this method has an advantage in calculating AC loss of the coil with a large number of turns.

Flux penetration and AC loss are among the key problems in the application of high-temperature superconductors (HTSs). Through simulation, the value and distribution of AC loss in HTS equipment can be evaluated and optimized in the design stage, so as to ensure the reliability and stability of the equipment. At present, there are many algorithms for AC loss calculation that can be simplified to a two-dimensional model, but for the case of three-dimensional structure such as cable in a spiral structure, there are still some problems such as difficult meshing, difficult convergence, and low efficiency. In this paper, an upgrade of the two-dimensional J model to a three-dimensional J model is proposed, permitting effective calculation of the flux penetration and AC loss in the CORC cable. The reliability of the method is verified by comparing the calculated results with the analytic model and with experimental results. At present, this method can efficiently calculate a 3D CORC model with a total of 15 superconducting tapes in five layers. Also discussed is the feasibility of upgrading to calculate larger models.

The Normal zone propagation velocity (NZPV) of a double-layer second generation high temperature superconducting wire manufactured by American Superconductor has been measured by electrical and thermal methods, and the results have been compared and discussed. The NZPV values determined by the voltage traces are ranging from 3.8 mm/s at 0.4 I _c to 19.2 mm/s at 0.9 I _c ; while from 5.9 to 18.3 mm/s by the temperature traces. NZPV determined by these two approaches agrees well with each other. Also, NZPV of double-layer YBCO tape is close to that of conventional single-layer superconducting tape.

The need for energy is growing as civilization develops. Superconductors have various benefits over regular conductors, including a high current-carrying density and nearly no resistance. Therefore, the objective that scientists continue to seek is the use of superconductors to replace traditional conductors in order to satisfy the demand for energy. As a key part of the superconducting electrical system, the critical current is one of the key properties of high-temperature superconducting (HTS) coils. Scholars have created a variety of numerical simulation models to estimate the performance of HTS coils. However, the extremely nonlinear E–J power law relationship that characterizes the voltage–current relationship in superconducting materials necessitates numerous iterative refinements during the coil design stage, which is time-consuming from the perspective of computing efficiency. Consequently, it is essential to increase computational efficiency. In this study, the critical current of HTS coils was calculated using the J model (integral method with the current density J as the state solution variable), and it was proved to be an efficient research method. The accuracy of the method is verified by comparing with the H model and the experimental measurement results of the critical current of the HTS coil. Moreover, compared with the reference finite element simulation model, this model has a speed advantage of at least four times, which is a good choice, especially, for HTS circular coils with large turns.

Since there is no iron core and the energy is only coupled through the primary and secondary windings, air-core transformers have advantages of no iron loss, no magnetic saturation, and compact in size, which make them attractive to be studied for practical applications. Due to its high current density and low loss, high temperature superconductor (HTS) brings additional advantages for this type of transformer. The HTS wires are highly magnetic field dependent and their characteristics are required for the HTS implementation and the design of the air-core transformers. As a result, magnetic field distribution of the HTS windings is researched, and its influence on the HTS critical currents, ac loss, and the transforming efficiency of the HTS air-core are analyzed.

Until recently, a new type of open magnetic shielding system was realized by the combination of a series of closed high temperature superconductor coils. We experimentally confirmed that the shielding factor (SF) of the new shielding system can reach more than 40 dB in the frequency spectrum of 0.1-16,000 Hz. Because of its superior ability to resist alternative magnetic field, we name the system Tesla-shielding (TS), to commemorate the father of alternative current (AC), Nikola Tesla. In this paper, we will report the design and realization of a Helmholtz coil based TS. The Helmholtz TS has many advantages over the previous planar TS. Especially, the Helmholtz TS has an engineering way of regulating the device for a better SF. We will introduce the design of the Helmholtz TS with the help of numerical simulation. The main electromagnetic properties of the TS, such as SF in the frequency spectrum and its shielding ability in the long duration measurement are given in this paper.