鉄紛製圧粉磁心の高周波磁気特性の解析

抄録

In order to clarify the factors determining the high frequency magnetic properties of compressed iron powder cores, complex permeability was calculated and compared with measured values.
Permeability at lower frequencies depends on the intrinsic permeability, effective demagnetization coefficient and packing fraction of iron powder particles. The effective demagnetization coefficient decreases with increasing packing fraction, and the permeability holds approximately a linear dependence on packing fraction.
Frequency dependence of complex permeability was calculated for two cases, assuming either intraparticle or inter-particle eddy currents. The results on the basis of intra-particle eddy currents are determined by the size, packing fraction, intrinsic permeability and conductivity of iron powder particles, while in the case of inter-particle eddy currents, the apparent DC permeability and conductivity of the core are the determining factors.
Measured values of complex permeability in the frequency range of 10 kHz-2 MHz coincide well with the calculation which gives larger core losses between the two cases. Accordingly the frequency dependency can be precisely predicted.