Combined Impact of Asymmetric Critical Current and Flux Diverters on AC Loss of a 6.5 MVA/25 kV HTS Traction Transformer

Wu, Yue; Song, Wenjuan; Wimbush, Stuart C.; Fang, Jin; Badcock, Rodney A.; Long, N.J.; Jiang, Zhenan

doi:10.1109/tte.2022.3194027

Cited by 10 publications

(4 citation statements)

References 70 publications

(51 reference statements)

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“…This was achieved by introducing magnetic flux diverters (MFDs) at the end-windings. We optimized the MFD design by considering different structural arrangements, size and minimizing the AC loss of the HTS winding using T-A and H formulations as noted in [34][35][36][37][38][39][40][41][42].…”

Section: Electromagnetic Designmentioning

confidence: 99%

“…However, a smaller winding height means that the winding in the radius direction will increase given the same number of turns so that the AC loss will grow and bring a severe burden to the refrigeration system. To solve this problem, we first studied how the AC loss depended on different winding structures [5,41,42] and then selected the winding structure whose AC loss via equation ( 5) was approximately 3 kW, allowing for the calculation of the short-circuit impedance by equation (6).…”

Section: Electromagnetic Designmentioning

confidence: 99%

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Design, development, and testing of a 6.6 MVA HTS traction transformer for high-speed train applications

Zhao

Fang

Jiang

et al. 2023

Supercond. Sci. Technol.

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High-temperature superconducting traction transformers (HTSTT) have the merits of small size and lightweight in comparison with their conventional counterparts. This article reports the development progress of a 6.6 MVA HTSTT operating at 65 K, including the design, testing, and system cooling. The introduction of flux diverters and an optimized winding design realized a short-circuit impedance higher than 43% and AC loss less than 3 kW. The insulation structure was designed to pass insulation tests specified in standard in China GB/T 25120-2010. An open cooling system with reduced pressure was developed, which realized the efficiency of the 6.6 MVA HTSTT above 99%. Before assembling the prototype transformer, we conducted tests for critical current and dielectric performance of the HTS double pancake coils (DPC) used in high-voltage (HV) and low- voltage (LV) windings to verify the current-carrying and insulation performances of each DPC. Finally, we measured the critical current and no-load loss of the HTSTT prototype at 77 K. Test results showed that the mass of the transformer is 33% less than conventional transformers. At 77 K, the critical current of the LV winding and HV winding is higher than 700 A and 50 A, respectively. Moreover, the HTSTT on a no-load test reached the test voltage of 25,000 V and loss of 6 kW. In the next step, we will continue to conduct experimental research, and verify the feasibility of the HTSTT on the train, and develop a circulating cooling system, all meeting the commercial requirements of the HTSTT. 

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Section: Electromagnetic Designmentioning

confidence: 99%

Section: Electromagnetic Designmentioning

confidence: 99%

Design, development, and testing of a 6.6 MVA HTS traction transformer for high-speed train applications

Zhao

Fang

Jiang

et al. 2023

Supercond. Sci. Technol.

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“…Using iron cores to achieve effective energy transfer and high magnetic field is common in high-temperature superconducting (HTS) power devices, particularly in transformers [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15], fault current limiters [16][17][18][19][20][21], and rapid-cycling synchrotrons [22,23]. For these superconducting applications, AC loss in superconductors caused by the motion of flux lines when carrying alternating currents or when exposed to magnetic fields remains a critical issue [21][22][23][24][25], as it poses challenges for cooling systems. When iron cores coupled with HTS coil windings are introduced in these applications, the magnetic field near the HTS coil windings changes due to the presence of iron cores, and the AC loss characteristics of HTS coil windings are influenced.…”

Section: Introductionmentioning

confidence: 99%

Experimental AC loss study on REBCO coil assemblies coupled with an iron cylinder

Wu,

Fang,

Miyagi

et al. 2024

Supercond. Sci. Technol.

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In HTS power devices, the presence of iron cores changes the magnetic field profile around the HTS coil windings, potentially affecting their AC loss characteristics. AC loss measurements for HTS coil windings coupled with an iron core using the electrical method can lead to a significant error, owing to the indirect estimation of the iron core loss through using a copper test coil. To investigate the cause of the experimental error and the influence of an iron core on coil AC losses, transport AC losses of REBCO double pancake coil (DPC) assemblies coupled with an iron cylinder were measured. A 40-turn 1DPC and an 80-turn 2DPC assembly wound with 4 mm SuperPower wire were employed in the measurements. To ensure the same iron core loss using the HTS coil assembly and the copper coil, 2D finite element method (FEM) simulations were conducted iteratively to design the iron core and the copper coil to get the same local magnetic field distributions in the designed iron core for the two cases. The main cause of the error is due to the difference in local magnetic flux densities in the iron core generated by the HTS coil assembly and the copper coil even when the ampere-turns of the coils are identical. We showed that the simulation-guided measurement method can assure accurate AC loss measurement in the HTS coil assemblies coupled with iron cores. Compared with the AC losses in the 1DPC and 2DPC coil assemblies without the iron cylinder, the presence of the iron cylinder significantly increases the coil losses. Frequency dependence is observed in the coil AC losses of the 1DPC and 2DPC assemblies when coupled with the iron cylinder. This is due to the eddy current induced in the iron cylinder generating a magnetic field, which influences the coil AC loss.

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“…To enable efficient energy transfer between HTS coil windings, a stronger mutual magnetic flux is desired. Therefore, an iron core with high magnetic permeability is usually used as a conduit to carry the flux between coils in many HTS applications, such as transformers [4], [5], [6], [7], [8], [9],…”

Section: Introductionmentioning

confidence: 99%

AC Loss Reduction in HTS Coil Windings Coupled With an Iron Core Using Flux Diverters

Fang

Amemiya

et al. 2023

IEEE Access

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Iron cores are widely employed in high temperature superconducting (HTS) power devices to enhance the magnetic field and improve the power density. In spite of these benefits, the presence of iron cores leads to a substantial increase in AC loss within HTS coil windings. Therefore, it is necessary to estimate the AC loss of HTS coil windings coupled with iron cores to propose methods for loss reduction. An effective way to reduce AC loss is to apply flux diverters (FDs) near the HTS coil windings. In this work, the 3D T -A homogenization method is used to calculate AC losses of the 1DPC (double pancake coil)-, 2DPC-, 4DPC-, and 8DPC assemblies at different currents with four ferromagnetic combinations: with an iron core (IC), with an iron core and FDs (IC_FDs), with an air core (AirC), and with air core and FDs (AirC_FDs). To weaken the impact of the iron core, the enlarged distance between the iron core and coil assemblies is considered to investigate AC loss dependence on this distance. In addition, the influence of the positions of FDs on AC loss reduction is also analyzed. The simulation results demonstrate that FDs can reduce the AC loss in coil assemblies, even when the iron core is present, owing to the reduction of the perpendicular magnetic field component in the end discs. For the 4DPC and 8DPC assemblies with IC, increasing the distance while using FDs, or decreasing the vertical gap between the coil assemblies and FDs, are effective in reducing AC loss.INDEX TERMS AC loss, superconducting coils, iron core, flux diverters, finite element method (FEM), 3D T-A homogenization method.YUE WU received the B.Eng. degree in electrical engineering and automation from the

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Combined Impact of Asymmetric Critical Current and Flux Diverters on AC Loss of a 6.5 MVA/25 kV HTS Traction Transformer

Cited by 10 publications

References 70 publications

Design, development, and testing of a 6.6 MVA HTS traction transformer for high-speed train applications

Design, development, and testing of a 6.6 MVA HTS traction transformer for high-speed train applications

Experimental AC loss study on REBCO coil assemblies coupled with an iron cylinder

AC Loss Reduction in HTS Coil Windings Coupled With an Iron Core Using Flux Diverters

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