Abstract: The present invention provides a boosting transformer for microwave oven, which is low in high-frequency loss, hardly saturated, small in size and easy to produce. The boosting transformer includes a rod-like ferrite core; and primary, secondary and heater windings wound around the rod-like ferrite core and piled up side by side in a direction of an axis of the rod-like ferrite core. It also includes a metal core formed from a long metal thin plate rolled by a plurality of times into a square-ring having one inner diameter larger than each of outer sizes of the primary, secondary and heater windings and the other inner diameter larger than a total size of the three windings piled up side by side, the metal core being arranged opposite to the rod-like ferrite core through a gap so as to be fitted toward the rod-like ferrite core from the outside of the primary, secondary and heater windings.

Abstract: An output choke for a D.C. arc welder comprising a high permeability core with an inductance controlling air gap defined by first and second pole pieces terminating in first and second surfaces facing each other and each having two spaced edges with an intermediate area, said surfaces converging from said intermediate area toward each of said edges to generate a specific cross sectional shape for said gap wherein said choke is large enough to carry at least about 100 amperes of weld current.

Abstract: A magnetic core has a toroidal configuration, formed by winding an iron-based amorphous metal ribbon. Thereafter the core is heat-treated to achieve a linear B-H characteristic. Advantageously, the linear B-H characteristic does not change with the level of magnetic fields applied and the frequency utilized. With such properties, the core is especially suited for use in a current transformer.

Abstract: Non-linear inductor(s) are used to reduce the percent total harmonic distortion of the harmonics in the line currents in the input side rectifier system of an ac drive system. Several constructions for the non-linear inductor(s) are described. The non-linear inductor(s) may be constructed from E and I laminations. The gap depends on the construction of the middle leg of the E laminations and may have a step with a constant spacing or a variable spacing which depends on the stacking of the laminations. Alternatively the non-linear inductor(s) may be constructed from a toriodal core that either has a step gap or a variable type gap.

Abstract: A core for a multi-phase transformer includes a body made of two or more rings having a common central axis. Each ring consists of a strip of magnetic permeable material wound about the central axis. The body is provided with a plurality of radially disposed windows, each window being bound by opposed axially extending legs and opposed circumferentially extending branches. The branches of each window are provided in respective axially adjacent rings, so that the branches and legs of each window define a closed magnetic circuit of substantially uniform magnetic permeability through which magnetic flux can circulate about the windows.

Abstract: An inductor component according to the present invention includes a magnetic core including at least one magnetic gap having a gap length of about 50 to 10,000 ?m in a magnetic path, a magnet for magnetic bias arranged in the neighborhood of the magnetic gap in order to supply magnetic bias from both sides of the magnetic gap, and a coil having at least one turn applied to the magnetic core. The aforementioned magnet for magnetic bias is a bonded magnet containing a resin and a magnet powder dispersed in the resin and having a resistivity of 1 ?·cm or more. The magnet powder includes a rare-earth magnet powder having an intrinsic coercive force of 5 KOe or more, a Curie point of 300° C. or more, the maximum particle diameter of 150 ?m or less, and an average particle diameter of 2.0 to 50 ?m m and coated with inorganic glass, and the rare-earth magnet powder is selected from the group consisting of a Sm—Co magnet powder, Nd—Fe—B magnet powder, and Sm—Fe—N magnet powder.

Abstract: Disclosed is a low-priced and small-sized magnetic core for an inductor suitable for a high frequency signal and a large-current signal. The magnetic core is modified from a conventional EP type magnetic core. A recess is integrally formed with a peripheral portion of the magnetic core when it is shaped. A bottom portion and the peripheral portion are extended toward an opening portion to an extent of about 70 percentages of a length measured from a center of the center portion to an internal surface of the peripheral portion. The peripheral portion opposite to the opening portion has a uniform thickness. The magnetic core is designed to facilitate its surface mounting onto a PCB.

Abstract: A distributed air gap material for a induction device in power systems for minimizing fringe losses, mechanical losses and noise in the core The distributed air gap material occupies a selected portion of the core and is formed of a finely divided magnetic material in a matrix of a dielectric material particles. The air gap material has a zone of transition in which the permeability values vary within the air gap material.

Abstract: Biased core devices and method of use are disclosed in which magnetic core energy losses due to hysteresis and eddy currents are greatly reduced in comparison to the core losses in prior art transformers and inductive devices. The present invention sets forth a transformer or choke device in which permanent magnets are surrounded by electrical steel materials and may be held in place by pole pieces. The magnetic core transformer structure also permits a method of use in which current passing through the device is controlled by the field strength of the permanent magnets. In addition, the biased magnetic core transformer operation may be linear or non-linear, and placed in series or parallel within a circuit. The magnetic components disclosed in the present invention affords both energy loss reductions and size reductions in comparison to known prior art transformers.

Abstract: A bulk amorphous metal inductive device comprises a magnetic core having at least one low-loss bulk ferromagnetic amorphous metal magnetic component forming a magnetic circuit having an air gap therein. The component comprises a plurality of similarly shaped layers of amorphous metal strips bonded together to form a polyhederally shaped part. The device has one or more electrical windings and is easily customized for specialized magnetic applications, e.g. for use as a transformer or inductor in power conditioning electronic circuitry employing switch-mode circuit topologies and switching frequencies ranging from 1 kHz to 200 kHz or more. The low core losses of the device, e.g. a loss of at most about 12 W/kg when excited at a frequency of 5 kHz to a peak induction level of 0.3 T, make it especially useful at frequencies of 1 kHz or more.

Abstract: An output choke for a D.C. arc welder comprising a high permeability core with an inductance controlling air gap defined by first and second pole pieces terminating in first and second surfaces facing each other and each having two spaced edges with an intermediate area, said surfaces converging from said intermediate area toward each of said edges to generate a specific cross sectional shape for said gap wherein said choke is large enough to carry at least about 100 amperes of weld current.

Abstract: A filter uses a special autotransformer that has a ferromagnetic core with a plurality of legs and flux return bars. A first coil is located on one leg, and a second coil is located on the same leg, but spaced from the first coil. The first coil and at least part of the second coil are connected in series to receive distorted alternating current and at least that part of the second coil is connected to an output terminal. Between the coils and extending at least part of the way from the first leg to an adjacent leg is a magnetic shunt assembly to divert part of the flux generated in the first coil by the alternating current so that that part does not link with the second coil. An air gap is located to link with the second coil to create an inductor in that coil by flux in the second coil, and a capacitor is connected across the second coil to tune it to the fundamental frequency of the alternating current and substantially reduce harmonics in that current.

Abstract: An inductor component is provided. The inductor component includes a core composed of a hollow core piece and a rod core piece, a bobbin, and bonded magnets. Regarding the hollow core piece and rod core piece, the rod core piece is arranged across the hollow core piece, and joining is performed between the bottom surfaces of both end portions of the rod core piece and the hollow core piece with bonded magnets therebetween.

Abstract: The current technology involved with overlaying any type of digital subscriber loop (xDSL) service with plain old telephone service (POTS) makes use of two separate transformers, one for POTS and another for xDSL. This invention provides a transformer which combines the POTS transformer and the xDSL transformer into one transformer. This considerably reduces the weight volume and cost of the overlaid POTS and xDSL circuits. In combining the two transformers the magnetic coupling between any one of the windings used for POTS and any one of those used for xDSL must remain weak despite their close proximity. In addition, any two windings of the same type of service, either POTS or xDSL, must remain strongly coupled. This is achieved by choosing a special geometric form for the core and choosing strategic locations for the windings. A portion of the core is dedicated to serve as a shunt for each component of the magnetic field produced by the windings.

Abstract: An inductor component according to the present invention includes a magnetic core including at least one magnetic gap having a gap length of about 50 to 10,000 &mgr;m in a magnetic path, a magnet for magnetic bias arranged in the neighborhood of the magnetic gap in order to supply magnetic bias from both sides of the magnetic gap, and a coil having at least one turn applied to the magnetic core. The aforementioned magnet for magnetic bias is a bonded magnet containing a resin and a magnet powder dispersed in the resin and having a resistivity of 1 &OHgr;·cm or more. The magnet powder includes a rare-earth magnet powder having an intrinsic coercive force of 5 KOe or more, a Curie point of 300° C. or more, the maximum particle diameter of 150 &mgr;m or less, and an average particle diameter of 2.

Abstract: In an inductor comprising an open magnetic path formed by a soft magnetic material and a winding provided around the open magnetic path, the soft magnetic material has its relative complex dielectric constant varying according to a frequency. In the soft magnetic material, the imaginary part of the relative complex dielectric constant is greater than the real part thereof in a high-frequency band equal higher than the frequency of the electric signal flowing in the winding. Specifically, the soft magnetic material has a resistivity of 150 &OHgr;m, has a real part of the relative complex dielectric constant, ranging from 1,000 to 20,000 at 1 kHz and 50 or less at 1 MHz, and the imaginary part is greater than the real part at 1 MHz.

Abstract: An inductance component includes a magnetic core (11, 12) forming a magnetic circuit having a magnetic gap, an exciting coil (14) wound around the magnetic core, and a permanent magnet (13) disposed in the magnetic gap. The permanent magnet is greater in sectional area than the magnetic core.

Abstract: An induction apparatus includes a winding arrangement having a winding start and a winding end for inducing a magnetic field in a magnetizable core; and a lossy, magnetizable device through which and/or about which the winding start and the winding end of the winding arrangement is so disposed as to induce a magnetic flux in the magnetizable device. This arrangement prevents an electric breakdown at the star point of winding strands of synchronous motors.

Abstract: An inductance component comprises a magnetic core having at least one magnetic gap, means for generating a direct-current biased magnetic field produced by mounting a permanent magnet in the vicinity of a generally closed magnetic circuit which passes through the magnetic gap in the magnetic core or on the outside thereof, and a coil wound around the magnetic core, wherein the permanent magnet is mounted near the magnetic gap at one or more legs of the magnetic core which sandwich the magnetic gap.

Abstract: Non-linear inductor(s) are used to reduce the percent total harmonic distortion of the harmonics in the line currents in the input side rectifier system of an ac drive system. Several constructions for the non-linear inductor(s) are described. The non-linear inductor(s) may be constructed from E and I laminations. The gap depends on the construction of the middle leg of the E laminations and may have a step with a constant spacing or a variable spacing which depends on the stacking of the laminations. Alternatively the non-linear inductor(s) may be constructed from a toriodal core that either has a step gap or a variable type gap.

Abstract: A wire wound core has windings which are wound in a single-layer winding fashion around substantially cylindrical body portions of bobbins. A gap is provided between the inner wall of a hole formed in the substantially cylindrical body portion of each bobbin and the outer peripheral surface of a leg portion of a corresponding core member by a rail-shaped rib disposed on the inner wall of the hole. Another gap is provided between the inner surface of an arm portion of the core member and the outer major of a flange portion of the bobbin by a convex spacer disposed on the outer major surface of the core member.

Abstract: A toroidal core for a toroid, including at least two toroidal rings that are stacked co-axially one upon another. At least one of the two toroidal rings has a body including a gap that forms a break in one side of the body. The gap avoids saturation of the core.

Abstract: Improved inductive apparatus having controlled core saturation which provides a desired inductance characteristic with low cost of manufacturing. In one embodiment, a pot core having a variable geometry gap is provided. The variable geometry gap allows for a “stepped” inductance profile with high inductance at low dc currents, and a lower inductance at higher dc currents, corresponding for example to the on-hook and off-hook states of a Caller ID function in a typical telecommunications line. In other embodiments, single- and multi-spool drum core devices are disclosed which use a controlled saturation element to allow for selectively controlled saturation of the core. Exemplary signal conditioning circuits (e.g., dynamically controlled low-capacitance DSL filters) using the aforementioned inductive devices are disclosed, as well as cost-efficient methods of manufacturing the inductive devices. An improved gapped toroid and an associated method of manufacturing is also disclosed.

Abstract: A silicon steel core spacing structure for improving induction comprises a shielded copper spacer between the magnetic flux sections of two silicon steel core, and the magnetic reluctance of such copper spacer is relatively low that can guide the traveling path of the magnetic line of force, and thus lower the magnetic flux density passing through the copper spacer. Therefore, the induction outputted from a transformer or a choke coil not only can comply with the safety tests, but also can improve the light-load power and the heavy-load power.

Abstract: The invention relates to an apparatus with a device for simultaneous transfer of electrical power and information between two components being movable to each other and preferably comprising a stationary and a movable component. According to the invention the apparatus includes a transfer device for the common transfer of power and information, with a primary coil arrangement (5, 6) mounted on one of the components and a secondary coil arrangement (11) mounted on the other component, a power supply (35, 41, 59) connected to the primary coil arrangement (5, 6) and based on pulse width modulation, and means (71, 72) for modifying signals generated by the power supply in dependence on the information to be transferred. The information can be transferred both from the one component to the other component and vice versa (FIG. 6).

Abstract: A bulk amorphous metal inductive device comprises a magnetic core having plurality of low-loss bulk ferromagnetic amorphous metal magnetic components assembled in juxtaposed relationship to form at least one magnetic circuit and secured in position, e.g. by banding or potting. The device has one or more electrical windings and may be used as a transformer or inductor in an electronic circuit. Each component comprises a plurality of similarly shaped layers of amorphous metal strips bonded together to form a polyhedrally shaped part. The low core losses of the device, e.g. a loss of at most about 12 W/kg when excited at a frequency of 5 kHz to a peak induction level of 0.3 T, make it especially useful for application in power conditioning circuits operating in switched mode at frequencies of 1 kHz or more. Air gaps are optionally interposed between the mating faces of the constituent components of the device to enhance its energy storage capacity for inductor applications.

Abstract: A transformer having an additional integrated inductor includes a first core (1) having at least a primary winding (5), a second core (2) having at least a secondary winding (4), and a third core (3), in which each core (1, 2, 3) is a separate component.

Abstract: A bulk amorphous metal inductive device comprises a magnetic core having plurality of low-loss bulk ferromagnetic amorphous metal magnetic components assembled in juxtaposed relationship to form at least one magnetic circuit and secured in position, e.g. by banding or potting. The device has one or more electrical windings and may be used as a transformer or inductor in an electronic circuit. Each component comprises a plurality of similarly shaped layers of amorphous metal strips bonded together to form a polyhedrally shaped part. The low core losses of the device, e.g. a loss of at most about 12 W/kg when excited at a frequency of 5 kHz to a peak induction level of 0.3 T, make it especially useful for application in power conditioning circuits operating in switched mode at frequencies of 1 kHz or more. Air gaps are optionally interposed between the mating faces of the constituent components of the device to enhance its energy storage capacity for inductor applications.

Abstract: A bulk amorphous metal inductive device comprises a magnetic core having at least low-loss bulk ferromagnetic amorphous metal magnetic component forming a magnetic circuit having an air gap therein. The device has one or more electrical windings and may be used as a transformer or inductor in an electronic circuit. The component comprises a plurality of similarly shaped layers of amorphous metal strips bonded together to form a polyhedrally shaped part. The low core losses of the device, e.g. a loss of at most about 12 W/kg when excited at a frequency of 5 kHz to a peak induction level of 0.3 T, make it especially useful for application in power conditioning circuits operating in switched mode at frequencies of 1 kHz or more. The component is fabricated by a process comprising cutting laminations of the requisite shape. The cut laminations are stacked and registered, and then bonded by an adhesive agent. The cutting of laminations is advantageously done with stamping or photolithographic etching techniques.

Abstract: A pencil ignition coil assembly module (40) that has a frusto-conically tapered core (46) and encapsulation (280) surrounding the side of the core. Features (216, 230, 234) center the core to a bobbin 48. A retainer (240, 240A) captures the core within the bobbin.

Abstract: A magnetic flux guiding apparatus comprises a conduit having a wall that comprises an electrically conducting material. An electrically insulating gap is formed in the wall along an entire length of the conduit. The electrically insulating gap prevents the conduit from having a closed electrical path that links any of the desired magnetic flux paths. For example, the electrically insulating gap can prevent the conduit from having a closed electrical path that surrounds a lengthwise axis of the conduit. The apparatus can also comprise a magnetic-field source that produces a magnetic flux that passes through an interior region bounded by the conduit. Where the conduit comprises a conventional electrically conducting material, the magnetic-field source can be a source of time-varying magnetic flux, such as an electrical coil.

Abstract: A converter with two coils and two magnetic gaps of which the upper and lower yokes of are two innerwardly concave plates or round plates. 3 set or more than 3 sets of axially magnetized permanent magnets are provided. Said permanent magnets are directly engaged with pole faces of said plates. Two magnetic gaps are formed between the vertical peripheric faces of said plates and the outer peripheric faces of a coaxial mounted annular or cylindrical magnetic body. Coils are inserted into said magnetic gap, while wound direction of two coils and the direction of current are decided to produce an electrodynamic force in the coils to the same direction. Said converter possesses resistance load characteristics by setting the values of the inductance of the two coils equal to each other in case that said converter are provided with two magnetic paths and coil circuits completely symmetric in their magnetic characteristics.

Abstract: A low-profile magnetic core capable of reducing the thickness of an inductor component is provided. The magnetic core includes at least one gap in a magnetic path, and a permanent magnet is inserted in the gap. The magnetic core has an alternating current magnetic permeability at 20 kHz of 45 or more in a magnetic field of 120 Oe under application of direct current, and has a core loss characteristic of 100 kW/m3 or less under the conditions of 20 kHz and the maximum magnetic flux density of 0.1 T. An inductor component is produced by applying at least one turn of coil to the aforementioned magnetic core.

Abstract: An inductor component contains a drum magnetic core made of a magnetic material having a structure including integrated flanges at both ends of a columnar material, a coil wound around the columnar material in the drum magnetic core and placed between the flanges, and a permanent magnet placed in the neighborhood of the drum magnetic core with the coil wound around. This inductor component contains a sleeve core fitted to the outside of the drum magnetic core. The permanent magnet is placed in at least one gap in a closed magnetic circuit formed with the drum magnetic core and the sleeve core in order to apply a direct-current magnetic field in the direction opposite to the direction of a magnetic field generated by a magnetomotive force due to the coil.

Abstract: A powder core is obtained by compaction-forming magnetic powder. The magnetic powder is an alloy comprising 1-10 wt % Si, 0.1-1.0 wt % O, and balance Fe. An insulator comprising SiO2 and MgO as main components is interposed between powder particles having a particle size of 150 &mgr;m or less.

Abstract: An inductor comprising a core, wherein the inductor is produced by the steps of: defining physical parameters of the core of the inductor, the physical parameters including dimensions of the air gap; defining a plurality of branches of the core; approximating the relative permeability of the core material by interpolating between first and second known values of magnetic flux density that exist in the core material when the core material is exposed to first and second values of magnetic field strength, respectively; calculating boundary currents that must flow through the inductor for each of the first and second known values of magnetic flux density to exist in each branch of the core; establishing the inductance of the inductor at each of the calculated boundary currents; and constructing the inductor.

Abstract: An electromagnetic inductor and transformer device and a method for making the same are disclosed. The device has a core that is separated into core sections along a dividing plane that extends essentially parallel to the magnetic field in the core. At least one cooling gap is formed between the core sections along the dividing plane to facilitate heat removal from the interior of the inductor and transformer device to the outside.

Abstract: In one example of a transformer, which is used in a dc-to-ac inverter circuit for lighting an electrical discharge lamp, a construction may be employed in which a primary winding and a secondary winding are gripped on both sides by a pair of cores composed of a magnetic material. In this transformer, a spacer is employed when forming a gap between the two cores. As a result, not only does the height dimension of the transformer grow large, but there is also a risk of the magnetic flux leaking from the spacer part to the outside.

Abstract: There is provided an inductive coupler for coupling a data signal to a phase line of a power line. The inductive coupler includes a split magnetic core having an aperture formed by an upper magnetic core and a lower magnetic core. The aperture permits the phase line to pass therethrough as a primary winding, the upper magnetic core is for making electrical contact with an outer surface of the phase line, and the lower magnetic core makes electrical contact with the upper magnetic core.

Abstract: A current transformer to be installed around a current-carrying conductor. The transformer has a split core with two parts, which can be opened to allow the transformer to be installed around or removed from the current-carrying conductor. A winding wound on the core is operatively connected to a switch so that the winding can be shorted prior to opening the split core when the transformer is removed from the current-carrying conductor in order to reduce the magnetic force holding the split core parts together. The winding is shorted by the switch prior to closing the split core parts when the transformer is installed around the conductor in order to minimize the damage to the core due to the induced magnetic force thereon. A mechanical tool is used to open or close the split-core parts. The switch can be linked to the tool for shorting and opening the winding.

Abstract: A slope gap inductor for reducing line harmonic currents. The slope gap inductor comprises a first inductor core portion, and a second inductor core portion positioned relative to said first inductor core portion so as to form an inductor gap, wherein the second inductor core portion includes a sloped gap surface that forms a sloped gap portion of the inductor gap having a varying gap height, and wherein the sloped gap surface has a slope value that is selected so that the slope gap inductor has a selected inductance value responsive to a level of current in the inductor.

Abstract: The invention relates to a magnetic component having at least two windings electrically connected in series (3, 4, 13, 14, 24-27, 31-33) and a core (1, 2, 10, 11, 20-23, 30) on which the windings (3, 4, 13, 14, 24-27, 31-33) are arranged so that in the event of a current flow through the windings (3, 4, 13, 14, 24-27, 31-33) the generated magnetic stray fields outside the component at least partly compensate each other, the core having at least one inside limb portion and at least two outside limb portions and in that the windings (3, 4, 13, 14, 24-27, 31-33) are arranged on the inside limb portion and/or the outside limb portions.

Abstract: A planar magnetic winding structure such as a transformer or inductor having an air gap in the core has a “keep away” region of 2 to 3 times the gap height in which there are no windings, reducing high frequency winding losses by 35 percent or more, without appreciable increases in low frequency winding losses. Such structures are useful, for example, in electronic ballasts for the lighting industry.

Abstract: An inverter transformer is formed of first and second cores arranged to face each other to form a closed magnetic circuit. The first core has a central leg, an outer perimeter wall, and a partition between the central leg and the outer perimeter wall so that a first groove is formed between the central leg and the partition and a second groove is formed between the partition and the outer perimeter wall concentrically with and outside the first groove. A primary winding is disposed in the second groove, and a secondary winding is disposed in the first groove so that the primary and secondary windings are arranged in the same plane.

Abstract: A method for forming a resin molding on a coil of a transformer is disclosed. The method comprises the steps of inserting a coil into an auxiliary spacing apparatus, inserting the auxiliary spacing apparatus into a mold, and forming a resin molding for the auxiliary spacing apparatus with the coil by putting a resin into the mold. According to the methods, the coil is not damaged and a resin molding is formed with a uniform thickness.

Abstract: A high frequency inductor includes a high permeability core, and at least one winding (6), having at least one winding layer (6). The core (2,3) exhibits at least one air-gap arranged within the at least one winding (6), whereat the at least one air-gap separates the core into at least two parts (2,3) and that a screen (14) is arranged around the at least one gap (4,4′,4″), between the winding (6) and the gap (4,4′4″). The screen is essentially concentric with the winding, and has a width which is equal to or wider than the width of the at least one gap (4,4′,4″).

Abstract: In an inductance component in which a cylindrical excitation coil (26) is fitted around a predetermined portion of a magnetic core (21) forming a magnetic path, a permanent magnet (25) is inserted into the magnetic path to apply a magnetic bias to the magnetic core. The permanent magnet is arranged outside the cylindrical excitation coil. It is preferable that the permanent magnet is spaced from the predetermined portion of the magnetic core along the magnetic path at least by a distance which corresponds to ½ of an average of inner diameters of the cylindrical excitation coil.

Abstract: There is disclosed a core structure with a very low profile, high power density and lower losses. Higher core surface area and improved core utilization in terms of flux density are other desirable feature in the disclosed design. The disclosed design also allowed for a larger core area where the DC fluxes are added, thereby reducing the air-gap requirements in the cores derived from low saturation density materials such as ferrites. The cellular nature of the design can also be effectively employed in vertically packaged power converters and modules.

Abstract: An inductance arrangement is directed to inductors, chokes and transformers with a very high power density. Chokes comprise a magnetic circuit and an electrical circuit, the latter usually comprising a copper winding. The inductance arrangement improves cooling of the magnetic circuit, efficiency of the induction arrangement, and reduces the consumption of material for the windings for a lower weight and a reduced structural size. Individual plate packs in the induction arrangement are displaced relative to each other to increase the surface area at both sides of the iron core. Displacement of the plates of the limbs allows for effective cooling passages or ducts between the core and the surrounding winding.

Abstract: Disposed in a magnetic gap of a magnetic core, a magnetically biasing permanent magnet is a bond magnet comprising rare-earth magnetic powder and a binder resin. The rare-earth magnetic powder has an intrinsic coercive force of 5 kOe or more, a Curie temperature of 300° C. or more, and an average particle size of 2.0-50 &mgr;m. The rare-earth magnetic power has a surface coated with a metallic layer containing an oxidation-resistant metal. In order to enable a surface-mount to reflow, the rare-earth magnetic powder may have the intrinsic coercive force of 10 kOe or more, the Curie temperature of 500° C. and the average particle size of 2.5-50 &mgr;m. In addition, to prevent specific resistance from degrading, the metallic layer desirably may be coated with a glass layer consisting of low-melting glass having a softening point less than a melting point of the oxidation-resistant metal.