Effect of electrical resistivity on core losses in soft magnetic iron powder materials

Iron powder should be electrically insulated with a dielectric to reduce eddy current losses in components fabricated by powder metallurgy intended for AC soft magnetic applications. However, most of the dielectrics act as distributed air gaps and reduce the apparent permeability of the material. To obtain materials with good magnetic properties, the dielectric amount should then be kept as low as possible while maintaining low eddy current losses. This paper presents the influence of electrical resistivity on core losses in iron powder compacts at low frequency (f < 1 kHz). The results obtained show that a resistivity one order of magnitude higher than the resistivity of iron (similar to 0.1 mu Omega m) is sufficient to maintain low eddy current losses in powder cores at frequencies below 100 Hz. (C) 1997 Elsevier Science B.V. All rights reserved.