Temperature compensation of ndfeb permanent magnets

Permanent magnet blocks of NdFeB have a relatively high maximum energy product. Because of its relatively low Curie temperature, however, NdFeB has a large temperature coefficient for its residual induction. The temperature coefficients of the relative magnetic fields ( D B/B)/D T in the air gap of NdFeB dipole magnets were reduced from-1.1 · 10-3/ ° C to less than 2 · 10-5/ ° C under operating temperatures of ± 6 ° C. This was achieved passively by using 1.25-mm-thick strips of 30%-Ni-Fe alloy as flux shunts for the NdFeB blocks. The magnets with soft-steel poles and flux-return yokes were assembled and measured in a temperature-controlled environment.