TY - Journal Article
AU - Vargas-Llanos, Carlos Roberto
AU - Zermeño, Victor M. R.
AU - Sanz, Santiago
AU - Trillaud, Frederic
AU - Grilli, Francesco
TI - Estimation of hysteretic losses for MgB2 tapes under the operating conditions of a generator
PY - 2016
PB - IOP Publishing
AB - Hysteretic losses in the MgB2 wound superconducting coils of a 550 kW synchronous hybrid
scaled generator were estimated as part of the European project SUPRAPOWER led by the
Spanish Fundación Tecnalia Research & Innovation. Particular interest was given to the losses
caused by the magnetic flux ripples in the rotor coils originating from the conventional stator
during nominal operation. To compute these losses, a 2D finite element analysis was conducted
and Maxwell’s equations written in the H-formulation were solved considering the nonlinear
material properties of the conductor materials. The modeled tapes are made of multiple MgB2
filaments embedded in a Ni matrix and soldered to a high purity copper strip and insulated with
Dacron braid. Three geometrical models of single tape cross sections of decreasing complexity
were studied: (1) the first model reproduced closely the actual cross section obtained from tape
micrographs. (2) The second model was obtained from the computed elasto-plastic deformation
of a round Ni wire. (3) The third model was based on a simplified cross section with the
superconducting filaments bundled in a single elliptical bulky structure. The last geometry
allowed the validation of the modeling technique by comparing numerical losses with results
from well-established analytical expressions. Additionally, the following cases of filament
transpositions of the multi-filamentary tape were studied: no transposition, partial and full
transposition; thereby improving understanding of the relevance of the tape fabrication process
on the magnitude of the determination of ac losses. Finally, choosing the right level of
geometrical detail, the following operational regimes of the machine and its impact on individual
superconducting tape losses in the rotor were studied: bias-dc current, ramping current under
ramping background field and magnetic flux ripples under dc background current and field.
SN - 0953-2048
UR - http://hdl.handle.net/11556/163
DX - 10.1088/0953-2048/29/3/034008
ER -