Composite Iron powder materials for the armature of axial-field permanent magnet machines

The properties of an iron powder/epoxy resin compact and its application as wedges in the armature of an axial-fleld d.c. machine are described. Compacts from carbonyl, electrolytic, and atomized iron powders are tested for their magnetic and electrical properties. Test results on carbonyl powder show that the saturation induction increases linearly with increase in the packing factor of the compact. Anisotropic behavior of compacts from electrolytic and atomized powders are investigated. Measured losses on the compacts show that for a frequency range of 200-1200 Hz, eddy-current losses are proportional to the square of frequency which shows a complete penetration of flux inside the particles. Wedges compacted from 96% atomized iron powder and 4% epoxy resin are incorporated in the armature which is tested in a machine having SmCo5magnets. The test results indicate that the application of the wedges reduces the circulating currents in the coils going under commutation. It was found that the magnetic losses in the wedges comprises only 2% of the total no-load losses. It was concluded that the losses introduced by the pulsating flux in the backing plate are predominant.