Analysis of Perpendicular Magnetic Fields on a 1 MVA HTS Transformer Windings With Flux Diverters

Abstract

In high temperature superconducting (HTS) transformer with double pancake windings, the perpendicular component of leakage magnetic flux density (B r ) applied to HTS tapes of double pancake windings is larger than that of solenoid windings, which acts as a cause to decrease the critical current in HTS tape and increase AC loss. In this paper, in order to reduce the B r applied to HTS windings, the use of ferrite flux diverters is presented. Flux diverters are located in between the primary windings and the secondary windings, and must be made of low-loss materials to minimize the heat. And electromagnetic analysis of a single-phase 1 MVA 22.9 kV/6.6 kV HTS transformer with flux diverters in HTS windings was accomplished. The variation of B r applied to the secondary windings and magnetic flux density in flux diverters were analyzed by changing their relative permeability of flux diverters respectively. Suitable relative permeability of flux diverters to reduce B r applied to HTS windings was selected, considering flux diverter losses by increment of B in flux diverters.Index Terms-Double pancake winding, flux diverter, HTS transformer.

Effect of double winding on loss characteristics of narrow stacked superconducting coils

“…Considering that the induced current in the windings generates a magnetic field,, a modified Kim formula is introduced to represent the critical current density [4], as shown in equation ( 9):…”

Numerical study on AC loss reduction of stacked HTS tapes by optimal design of flux diverter

“…Although many studies on AC loss reduction using a magnetic flux diverter have been carried out [5,7,[14][15][16][17], to the best of our knowledge, few works have provided the detailed mechanism behind AC loss reduction caused by a flux diverter. Here, the AC losses per turn for four typical cases listed in table 2 are compared, as shown in figure 12.…”

“…Taking the anisotropic magnetic field dependence of the AC loss into account, one way of decreasing AC loss in HTS coils is using ferromagnetic material to divert magnetic flux orientation to be as parallel as possible to the tape surface. Therefore, magnetic materials have been widely employed in HTS AC applications, such as transformers [7,8], cables [9], superconducting magnetic energy storage [10] and fault current limiters [5,11], in order to reduce the AC loss.…”

AC loss measurement and simulation in a REBCO coil assembly utilising low-loss magnetic flux diverters

“…The use of ferromagnetic flux diverters is another effective method to reduce AC loss in HTS coil windings comparable to using low loss conductors. Flux diverters are used to reshape the flux distribution around coil windings to reduce AC loss or increase critical current of DC coil windings [17][18][19][20][21][22][23][24][25][26][27][28]. Previous studies have proven that magnetic flux diverters (MFDs) can reduce AC loss in Bi-2223 coils [18,23,24].…”