A dual-molding magnet rotor was evaluated as a soft magnetic composite for the magnetic material of the rotor of a motor. Especially the possibility of using a dual-molding magnet rotor as means to improve motor efficiency was investigated. A dual-molding magnet rotor was a one-piece permanent magnet rotor made with bonded NdFeB magnet and soft magnetic composite core. A permanent-magnet synchronous motor was targeted for evaluation, and three types of dual-molding magnet rotors with different magnetic orientations were evaluated using the finite element method (FEM) and a trial model of test motor. It was confirmed that the cogging torque originated in the variation of the rotor element decreased because the pole-pitch accuracy and the outer-size accuracy were improved by utilizing a one-piece molding in the dual-molding magnet rotor. In spite a difference in the maximum energy products of the three magnets of about three times, the difference between maximum efficiency of the sintered rare-earth radial ring magnet and the isotropic-multi-pole oriented magnet and that between the former and the anisotropic-pole-concentrate oriented magnet are within 1%. The evaluation results show that the structure of dual-molding-magnet-rotor is superior to sintered rare-earth radial ring magnet rotor.Index Terms-bonded magnet, soft magnetic composite, magnetic characteristics, permanent-magnet motor 1-4244-1298-6/07/$25.00 漏2007 IEEE.
The wire antenna loaded with alumina was designed for the lower hybrid resonance heating in a small toroidal machine. The antenna impedance was calculated by the electromotive force method using the variational principle and found to be large enough to match with the r.f. source through usual transmission lines. The power spectrum was well behaved to satisfy the so-called accessibility condition in terms of the refractive index along the static magnetic field. Electron heating as well as ion heating is possible because the spectrum of radiated slow wave can be controlled by the selection of the thickness to the alumina cover. Alumina serves as an insulator against breakdown as well as a retarder of waves.
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