Bi2223 tapes were investigated by transport and magnetic measurements.
Two different regimes concerning the field dependence of the critical
current density J(c) are obtained At T greater-than-or-equal-to 6K J(
c) follows an exponential law. From analysis of magnetic relaxation me
asurements by means of distributions of activation energies an explana
tion of the low temperature behaviour of J(c) in terms of a change in
pinning behaviour is possible.