Isamu Otsuka

Magnetic Properties of Fe-Based Amorphous Powders With High-Saturation Induction Produced by Spinning Water Atomization Process (SWAP)

Fe-based amorphous powders with high magnetic flux density were fabricated in an extremely high cooling rate of over 10 ⁶ K/s by spinning water atomization process (SWAP). The composition of the alloys studied were Fe ₇₉(Si _0.5B _0.5) ₁₉C ₂ and Fe _x(Si _0.3B _0.7) _98-xC ₂ (x = 79,80,81,83,84). The saturation flux density Bs increased with increasing iron content. For Fe ₈₃(Si _0.3B _0.7) ₁₅C ₂, the Bs value was 1.64 T, which is 31% higher than that of our previously developed (Fe _0.97Cr _0.03) ₇₆(Si _0.5B _0.5) ₂₂C ₂ alloy. Furthermore, consolidated cores of amorphous powders were also fabricated by compact-pressing techniques.

Magnetic Properties of Fe-Based Amorphous Powder Cores With High Magnetic Flux Density

Fe₈₁(Si_0.3B_0.7)₁₇C₂ amorphous powder cores with glass binder were fabricated by compact-pressing techniques, and the relation between magnetic properties and powder particle sizes was evaluated. The Fe₈₁ (Si_0.3B_0.7)₁₇C₂ powder core exhibited superior magnetic properties compared with our previously developed (Fe_0.97Cr_0.03)₇₆ (Si_0.5 B_0.5 )₂₂C₂ powder core. The magnetic flux density Bm of the core made of Fe₈₁ system powders at 20 000 A/m was about 29% higher than that of Fe₇₆ system core. The core loss decreased with decreasing particle sizes. For the core made of powders with mean particle size of 22 mum below 45 mum in diameter, the loss at 100 kHz for Bm = 0.1 T was 520 kW/m³. This value was comparable to that of Fe₇₆ system powder core with a lower flux density. In addition, fairly superior characteristics of permeability under dc bias field were also attained. The values of Fe₈₁ system core was about 10% higher than that of Fe ₇₆ system almost over the entire range measured.

Magnetic properties of compressed amorphous powder cores and their application to a fly-back converter

Fe-based amorphous powder cores with glass binder were fabricated by hot-pressing techniques. The cores exhibited low core losses, relatively low effective permeability and high flux density, which are superior magnetic properties when applied to choking coil or fly-back transformers operating in the high frequency range. The core obtained was applied to a fly-back converter working at 100 kHz. The conversion efficiency examined at output power up to 300 W was higher than that of converters using a typical commercial Sendust core and a single gap ferrite core.