Numerical study of AC loss of two-layer HTS power transmission cables composed of coated conductors with a ferromagnetic substrate

WOS: 000412571400004This work includes the simulation of hysteretic AC losses in two-layer HTS power transmission cables made of second-generation high-temperature superconducting tapes with a ferromagnetic substrate subject to an oscillating AC transport current, calling upon the COMSOL Multiphysics finite-element software program and exploiting an AC/DC module. How the AC transport loss is influenced by the arrangement of tapes, as well as the optimized design of superconducting power cables based on YBCO-coated conductors, are investigated. According to the radial arrangement of the tapes, four different orientations of ferromagnetic substrate are considered: 1) out-in (substrate of inner/outer layer facing outward/inward), 2) in-out (substrate of inner/outer layer facing inward/outward), 3) in-in (substrates of both inner and outer layers facing inward), and 4) out-out (substrates of both inner and outer layers facing outward). We found that the AC loss of the superconducting layer for the out-in arrangement is the lowest. We also compare our calculations with experimental results.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [110T876]This work was fully supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under grant number 110T876

A Comparative Study of AC Transport and Eddy Current Losses for Coil Made of HTS Tapes Coated with Copper Stabilizer

WOS: 000412085400040In this work, the evaluation of AC loss of the pancake coils wound by HTS-coated conductors, by employing the finite element method in 2D, is presented. The transport current loss of the superconducting tape and the eddy current loss of the copper stabilizer as a function of the amplitude for four frequencies of the applied current are examined numerically by utilizing a newly developed calculation method based on the A - V formulation embedded in COMSOL Multiphysics software with an AC/DC module. The number of the coil turn is 10, and the radius is about 60 mm. The superconducting layer width and height in the simulations are 12 and 1 mm, respectively. The width and height of the copper layers are 12 and 80 mm, respectively. The critical current density of tapes is taken as 300 A.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [114F424]This study is supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under the grant number 114F424

AC Loss Calculation of Synchronous Generators Made of HTS Superconducting Armature Windings and Permanent Magnet Rotor

International audiencein this study, a novel FEM calculation method based on A-Formulation of Maxwell Equations was proposed to evaluate the transient AC current losses of superconducting generators. The calculations are carried out in 2-Dimensions. The model generator under consideration is a three-phase synchronous generator with a 12-pole and 12-slot rotor made of permanent magnets and the stator windings made of high-temperature superconducting coils. Superconducting coils are wound with 2G HTS coated conductors and the critical current intensity is around 300 A at T = 77 K. Rotor magnets generate magnetic fields in the xy-plane and only current is induced in the z-direction inside the HTS coils. The Loss calculation of the superconducting generator were then repeated with the H-formulation and the A-H Hybrid model. AC loss was calculated for different rotor speeds using all three calculation approaches. The induced current distributions and magnetic field distributions in HTS coils for various time instants for 60 rpm rotor sped are presented

AC Loss Calculation of Synchronous Generators Made of HTS Superconducting Armature Windings and Permanent Magnet Rotor

International audiencein this study, a novel FEM calculation method based on A-Formulation of Maxwell Equations was proposed to evaluate the transient AC current losses of superconducting generators. The calculations are carried out in 2-Dimensions. The model generator under consideration is a three-phase synchronous generator with a 12-pole and 12-slot rotor made of permanent magnets and the stator windings made of high-temperature superconducting coils. Superconducting coils are wound with 2G HTS coated conductors and the critical current intensity is around 300 A at T = 77 K. Rotor magnets generate magnetic fields in the xy-plane and only current is induced in the z-direction inside the HTS coils. The Loss calculation of the superconducting generator were then repeated with the H-formulation and the A-H Hybrid model. AC loss was calculated for different rotor speeds using all three calculation approaches. The induced current distributions and magnetic field distributions in HTS coils for various time instants for 60 rpm rotor sped are presented

A Novel Method for Numerical Analysis of Microwave Surface Resistance of Type-II Superconductors

WOS: 000370948300001Microwave surface resistance of type-II superconductors is investigated via the finite-element method by calculating the electromagnetic field distribution within a superconductor. The software allows changing the geometrical parameters in a facile way. Using a finite-element procedure and the approximation by Bonura et al. [Eur. Phys. J. B 52 (4), 459 (2006); Eur. Phys. J. B 53 (3), 315 (2006)], it is shown that the microwave surface resistance of type-II superconductors can be numerically calculated in the framework of the critical-state model.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [111T715]This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under Grant 111T715. This paper was recommended by Editor-in-Chief B. Plourde

Two-Dimensional Finite-Element Analysis of Pinning-Induced Stress in HTS Power Transmission Cables Made of 2G Superconducting Tapes With and Without Magnetic Substrate

WOS: 000376104100001In a two-layer superconducting cable, we numerically investigated the effect of magnetic properties and alignment of the substrates of the tapes on the stress distribution induced by a very high transported electric current. The calculations are carried out for two tapes, with one being on top of the other. Sharp peaks of induced stress very close to the edges of the tapes are observed. When nonmagnetic substrates are used, the stress distributions on the tapes are almost identical, as well as being much lower than those in the cases involving ferromagnetic (FM) substrates. When the tapes are arranged face to face with FM substrates on the outer sides, the stress distribution arisen in the outer tape is considerably higher than that in the inner tape. In contrast, flipping both layers, so that the tapes are back to back, gives rise to a much lower stress over the outer tape than that over the inner tape.Scientific and Technological Research Council of Turkey (TUBITAK)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [110T876]This work was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) under Grant 110T876. This paper was recommended by Editor L. Chiesa

Treatment delays and in-hospital outcomes in acute myocardial infarction during the COVID-19 pandemic: A nationwide study

Objective: Delayed admission of myocardial infarction (MI) patients is an important prognostic factor. In the present nationwide registry (TURKMI-2), we evaluated the treatment delays and outcomes of patients with acute MI during the Covid-19 pandemic and compaired with a recent pre-pandemic registry (TURKMI-1). Methods: The pandemic and pre-pandemic studies were conducted prospectively as 15-day snapshot registries in the same 48 centers. The inclusion criteria for both registries were aged ≥18 years and a final diagnosis of acute MI (AMI) with positive troponin levels. The only difference between the 2 registries was that the pre-pandemic (TURKMI-1) registry (n=1872) included only patients presenting within the first 48 hours after symptom-onset. TURKMI-2 enrolled all consecutive patients (n=1113) presenting with AMI during the pandemic period. Results: A comparison of the patients with acute MI presenting within the 48-hour of symptom-onset in the pre-pandemic and pandemic registries revealed an overall 47.1% decrease in acute MI admissions during the pandemic. Median time from symptom-onset to hospital-arrival increased from 150 min to 185 min in patients with ST elevation MI (STEMI) and 295 min to 419 min in patients presenting with non-STEMI (NSTEMI) (p-values <0.001). Door-to-balloon time was similar in the two periods (37 vs. 40 min, p=0.448). In the pandemic period, percutaneous coronary intervention (PCI) decreased, especially in the NSTEMI group (60.3% vs. 47.4% in NSTEMI, p<0.001; 94.8% vs. 91.1% in STEMI, p=0.013) but the decrease was not significant in STEMI patients admitted within 12 hours of symptom-onset (94.9% vs. 92.1%; p=0.075). In-hospital major adverse cardiac events (MACE) were significantly increased during the pandemic period [4.8% vs. 8.9%; p<0.001; age- and sex-adjusted Odds ratio (95% CI) 1.96 (1.20-3.22) for NSTEMI, p=0.007; and 2.08 (1.38-3.13) for STEMI, p<0.001]. Conclusion: The present comparison of 2 nationwide registries showed a significant delay in treatment of patients presenting with acute MI during the COVID-19 pandemic. Although PCI was performed in a timely fashion, an increase in treatment delay might be responsible for the increased risk of MACE. Public education and establishing COVID-free hospitals are necessary to overcome patients' fear of using healthcare services and mitigate the potential complications of AMI during the pandemic. © 2020 by Turkish Society of Cardiology