Transient field losses in multifilamentary composite conductors carrying transport currents

Investigations of the losses in multifilamentary composite conductors which result from the simultaneous change of the external field B
e
and transport current I are presented. The total loss is best characterized by a maximum normalized transport current i
m
= I
m
/I
c
(I
c
= critical current) and a dimensionless field-change rate
\beta = \tau\dot{B}_{e}/B_{p}
, where τ is the relaxation time of the coupling current and B
p
is the full-penetration field of a solid superconductor equivalent to the multifilamentary composite. For
\beta \gsim 1
, the composite conductor behaves like a solid and a saturation effect occurs in the loss. The characteristic feature of the composite appears only for
\beta \lsim 1
. The increase in losses arising from the non-zero transport current theoretically, is not larger than about 30 percent. For practical calculations, the experimental results over a wide range of β and i
m
agree well with the theory.