Hitachi Metals, Ltd.

Hitachi, Ltd.

Masahiko Fukui

Masao Ogata

Hiromi Sako

Yasuji Kamata

There is provided a gap in a magnetic circuit of an iron core inductor, and a plurality of small size permanent magnet pieces are placed in the aforesaid gap, with the magnetizing directions thereof being provided in side-by-side relation. If the magnetizing direction of the permanent magnet pieces is opposed to that of a D.C. magnetic field which is produced in a magnetic circuit, yet in case D.C. and A.C. overlapping currents flow through the inductor, then the D.C. magnetic field produced in the magnetic circuit will be off-set thereby, providing a high inductance value, while eddy currents produced within the permanent magnet pieces due to the A.C. magnetic field will be reduced to a considerable amount, because the permanent magnet pieces are small in size, thus minimizing the heat to be produced in the permanent magnet pieces.

Inductor with plurality of magnet pieces in air gap

An inductor having a coil member commonly wound on a couple of closed magnetic circuits made of a soft magnetic material. A magnetic gap is provided at a part of the soft magnetic material of at least one of the two closed magnetic circuits, and a permanent magnet providing a magnetic bias is inserted in the magnetic gap. This inductor is used in series between a DC power source providing a superimposed current of a DC current and an AC current and a load. The inductance of the inductor is very large with respect to a small DC current, while it reduces sharply when the applied DC current increases to be a certain value to show a substantially constant low value with respect to a DC current value beyond the certain value.

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Kumagaya, Japan

Masahiko Fukui