A reactor includes a coil having a winding portion, and a magnetic core including a core piece having an inner core portion disposed inside the winding portion. The core piece is a compact made of a composite material that contains a magnetic powder and a resin. The reactor further includes: a first projection that is integrated with and projects from an outer peripheral face of the inner core portion, and comes into contact with an inner peripheral face of the winding portion so as to position the winding portion in a diameter direction of the winding portion, and a second projection that is integrated with and projects from the core piece at a position opposing an end face of the winding portion, and comes into contact with the end face of the winding portion so as to position the winding portion in an axial direction thereof.

An antenna module according to one embodiment of the present invention, comprises: a coil layer including a wound first coil; a shield layer disposed on the coil layer and including a plurality of sequentially stacked magnetic sheets; and a protection layer disposed on the shield layer, wherein the thickness of an edge of the shield layer is greater than the thickness of the center of the shield layer, and the total separation distance between the plurality of magnetic sheets at the edge of the shield layer is greater than the total separation distance between the plurality of magnetic sheets at the center of the shield layer.

A dust core includes large particles having an average particle size of 8-15 μm, medium particles having an average particle size of 1-5 μm, and small particles having an average particle size of 300-900 nm when a cross section thereof is observed. An area ratio occupied by the large particles is 50% to 90%, an area ratio occupied by the medium particles is 0% to 30%, and an area ratio occupied by the small particles is 5% to 30%, when a total area ratio occupied by the large particles, the medium particles and the small particles is 100% in the cross section. Vickers hardness (Hv) of the large particles, the medium particles and the small particles is 150-600 respectively. The small particles are alloy powder containing Fe and at least Si or N. The dust core may be included in an inductor element.

A dust core includes large particles having an average particle size of 8-15 μm, medium particles having an average particle size of 1-5 μm, and small particles having an average particle size of 300-900 nm when a cross section thereof is observed. An area ratio occupied by the large particles is 50% to 90%, an area ratio occupied by the medium particles is 0% to 30%, and an area ratio occupied by the small particles is 5% to 30%, when a total area ratio occupied by the large particles, the medium particles and the small particles is 100% in the cross section. Vickers hardness (Hv) of the large particles, the medium particles and the small particles is 150-600 respectively. The small particles are alloy powder containing Fe and at least Si or N. The dust core may be included in an inductor element.

A soft magnetic powder contains a particle having a composition represented by Fe.sub.xCu.sub.aNb.sub.b(Si.sub.1-yB.sub.y).sub.100-x-a-b, and 0.3≤a≤2.0, 2.0≤b≤4.0, and 72.5≤x≤75.5, and y is a number satisfying f(x)≤y≤0.99, and f(x)=(4×10.sup.−34)×17.56. The particle includes a crystal grain having a grain size of 1.0 nm to 30.0 nm, a Cu segregation portion, and a crystal grain boundary. A content proportion of the crystal grain is 30% or more. When the Cu segregation portion positioned in a surface layer portion and having a grain size of 1.0 nm to 5.0 nm is referred to as a first Cu segregation portion, and the Cu segregation portion positioned in an inner portion and having a grain size of 3.0 nm to 10.0 nm is referred to as a second Cu segregation portion, a number proportion of the first Cu segregation portion is 80% or more, and a number proportion of the second Cu segregation portion is 80% or more.

A soft magnetic powder contains a particle having a composition represented by Fe.sub.xCu.sub.aNb.sub.b(Si.sub.1-yB.sub.y).sub.100-x-a-b, and 0.3≤a≤2.0, 2.0≤b≤4.0, and 72.5≤x≤75.5, and y is a number satisfying f(x)≤y≤0.99, and f(x)=(4×10.sup.−34)×17.56. The particle includes a crystal grain having a grain size of 1.0 nm to 30.0 nm, a Cu segregation portion, and a crystal grain boundary. A content proportion of the crystal grain is 30% or more. When the Cu segregation portion positioned in a surface layer portion and having a grain size of 1.0 nm to 5.0 nm is referred to as a first Cu segregation portion, and the Cu segregation portion positioned in an inner portion and having a grain size of 3.0 nm to 10.0 nm is referred to as a second Cu segregation portion, a number proportion of the first Cu segregation portion is 80% or more, and a number proportion of the second Cu segregation portion is 80% or more.

A battery pack charging system includes a battery pack interface configured to receive a battery pack, a charging circuit coupled to the battery pack interface to provide charging current to the battery pack interface, and a controller coupled to the charging circuit and configured to control supply of charge current to the battery interface. The battery pack charging system further includes a power supply circuit coupled to the charging circuit, a filter circuit coupled to the power supply circuit and including a nanocrystalline ferrite common mode choke, and an alternating current plug configured to connect the filter circuit to an alternating current power source.

A soft magnetic alloy powder includes soft magnetic alloy particles having an amorphous phase. Each of the soft magnetic alloy particles has chemical composition represented by Fe.sub.aSi.sub.bB.sub.cC.sub.dP.sub.eCu.sub.fSn.sub.gM1.sub.hM2.sub.i, where M1 is one or more elements of Co and Ni, M2 is one or more elements of Ti, Zr, Hf, Nb, Ta, Mo, W, Cr, Al, Mn, Ag, V, Zn, As, Sb, Bi, Y, and a rare earth element, and 79≤a+h+i≤86, 0≤b≤5, 7.2≤c≤12.2, 0.1≤d≤3, 7.3≤c+d≤13.2, 0.5≤e≤10, 0.4≤f≤2, 0.3≤g≤6, 0≤h≤30, 0≤i≤5, and a+b+c+d+e+f+g+h+i=100 (parts by mol) are satisfied.

A ferrite core includes a ferrite sintered body in which integrally formed are a winding core portion, extending in a lengthwise direction, and flange portions provided at both ends in the lengthwise direction of the winding core portion and projecting from the winding core portion in at least a height direction orthogonal to the lengthwise direction. Pores are present inside the winding core portion and the flange portions, and an abundance ratio of the pores in the winding core portion is equal to or more than about 0.05% and equal to or less than about 1.00% (i.e., from about 0.05% to about 1.00%).

Systems and methods for improving winding losses in transformers are disclosed. In one aspect, a transformer includes a first magnetic core having an interior portion and an exterior portion, a second magnetic core in contact with the interior and exterior portions, a plurality of primary and secondary windings formed around the interior portion, where the interior portion is formed from one of a first magnetic material and a second magnetic material, and the exterior portion is formed from one of the first magnetic material and the second magnetic material, where the first magnetic material has different properties than the second magnetic material. In another aspect, the first magnetic core includes a third portion that extends across and is in contact with the interior portion and the exterior portion, where the third portion is formed from one of the first magnetic material and the second magnetic material.