Abstract
Exchange-coupled nano-composite melt-spun powder is a nano-stroctured composite of soft and hard magnetic phases mutually coupled by exchange interaction at the grain boundaries. Its resource balance and resistance to oxidation are better than those of Nd2Fe14B stoichiometric composition melt-spun powder, because it contains a smaller proportion of rare-earth elements such as neodymium. In order to apply this powder to high-efficiency small IPM (interior permanent magnet) brushless motors, we developed a modified molding technique using the slip-flow mechanism, which allows high-density molding of nano-composite melt-spun powder exceeding 95 wt%. This technique was used to develop a small IPM rotor by directly molding the melt-spun powder with a laminated steel core. IPM motors using the above-mentioned rotor were found to have adequate stability with respect to aging and reverse magnetic fields, as well as high efficiency.
