Design and testing electric devices with soft magnetic composites
Insulated iron powder when compacted and heat treated offer an attractive alternative to conventionally used steel laminations in components requiring soft magnetic materials. Net shaped parts in a single operation make it possible to construct electrical machines with 3-dimensional magnetic fields, while allowing reduced production costs. In addition, unique design freedoms with significant benefits result from their isotropic magnetic properties. Nevertheless, dielectromagnetics account for a small fraction of the total number of magnetic components used, due to a lack of information available on the characteristics of such materials. In an effort to enhance their usability, tests were conducted on inductors' cores made of different kinds of dielectromagnetics and the influence of geometry on their magnetic properties was examined. Furthermore, the total energy loss was measured under different working conditions, such as temperature and frequency. The tests were conducted on ring specimens made of iron powder with addition of 0.1% or 0.5% dielectric and the results gave valuable insights on the underlying mechanisms affecting power dissipation. The hysteresis loss seemed to be the one having the most significant influence on the decrease of dielectromagnetics' total energy loss with increase of temperature. In fact, at 5Hz less than 7% decrease of total energy loss was observed between 24°C and 100°C. Sufficient insulation induced by the presence of dielectric between iron particles confirmed weak resistivity change in the examined samples. In addition, the possibility to design magnetic cores of different shapes and sizes without concern for the deterioration of magnetic properties was established. The knowledge of these properties is necessary for the correct calculation of magnetic circuits and has an essential influence on the final design and parameters of electrical machines. The success would lie in magnetic circuit design exploiting the unique shaping possibilities offered by the soft magnetic composite (SMC) technology.