A primary coil which includes a primary winding which is wound around a primary bobbin, and a secondary coil which includes a secondary winding which is separately wound around a secondary bobbin which includes a plurality of sections, are provided, and a winding portion of the secondary coil is configured in a state where a maximum winding height is set as 20% through 30% with respect to an axis length winding length.

An ignition coil has a ferromagnetic core, a primary coil surrounding a portion of the core and wrapped helically with a conductor, a winding form having partitions extending outwardly of a tubular surface of the winding form, and a secondary coil wrapped on the winding form. The partitions define a plurality of annular coil chambers including central chambers and end chambers. The end chambers have a spiral land. The secondary coil includes coil sections in each of the plurality of coil chambers. The secondary coil has coil turns in the end chambers in a spiral configuration on the spiral land and increasing progressively in diameter toward the central chambers.

A coil component includes a drum core as a first core and a top plate as a second core. The coil component also includes a wire and an adhesive. The adhesive includes a bisphenol F resin, magnetic powder, and a curing agent. A cross section perpendicular to an adhesion surface between the adhesive and the drum core is set to a specific cross section. A direction perpendicular to the adhesion surface is set to a thickness direction. A direction perpendicular to the thickness direction in the specific cross section is set to an extending direction. The adhesive includes a resin portion in the specific cross section. The resin portion is a portion which does not contain the magnetic powder in the thickness direction in a range between the drum core and the top plate and which is continuously disposed by 3 m or larger in the extending direction.

A coil device includes a bobbin, a first winding part, and a second winding part. A partition portion is formed on an outer peripheral surface of the bobbin. The first winding part is wound around the outer peripheral surface at one side of the partition portion. The second winding part is wound around the outer peripheral surface at the other side of the partition portion and has an inner winding layer and an outer winding layer located farther to the outer peripheral surface at the other side than the inner winding layer.

In an embodiment, an inductive component includes at least one electrical conductor, a coil former with a hollow-shaped winding former, on a surface of which the at least one electrical conductor is wound around the winding former, a magnetic core arranged in a first cavity of the winding former and a potting material, wherein the at least one electrical conductor is surrounded by the potting material, wherein the potting material has no directly adherent contact with the magnetic core, wherein the magnetic core comprises a first part-body and a second part-body, which are connected to one another, wherein at least one of the first part-body or the second part-body of the magnetic core comprises a leg arranged in the first cavity of the winding former and at least one further leg arranged outside the first cavity of the winding former.

A transformer including first coil unit and second unit, wherein one or more coils are wound on the bobbin of insulating material in at least one of the first coil unit and the second unit, and wherein the bobbin is formed with at least one partitioning flange for partitioning a coil winding surface of the bobbin into two winding surfaces along the longitudinal direction of the bobbin, is disclosed.

A bobbin has a winding core and multiple partitioning walls, so that multiple winding areas are formed in an axial direction. A groove is formed in each of the partitioning walls, so that a wire rod strides over the partitioning wall bypassing through the groove when a winding process for one of the winding areas is finished and a winding process for a neighboring winding area will be started. The groove has a first and a second guide wall surfaces, which are opposed to each other in a circumferential direction. Each of the first and the second guide wall surfaces is inclined in the axial direction such that each of the first and the second guide wall surfaces comes closer to a circumferential winding-end side in the axial direction to a stride-end side.

The main assembly of a leakage transformer includes a bobbin which includes collar/collars adjacent to location/locations corresponding to a winding edge of a primary coil and/or a secondary coil wound around the bobbin. The collar includes a first collar separating the primary coil and the secondary coil from each other in an axial direction. The leakage transformer includes a bottomed casing within which the main assembly is received and embedded in a filling material. At least one of the collar/collars have a coil facing surface that is formed with a pattern of concavity and convexity. The pattern includes a plurality of protrusions and recesses extending substantially parallel to each other in a longitudinal direction. The recesses of the collar extend in the longitudinal direction and represent channels resembling grooves through which the filling material is passed and guided into the coils present in their vicinity.

A transformer in which the high-voltage and low-voltage coils are easily laminated when they are alternately laminated in their axial directions, improving power efficiency. The transformer includes: a high-voltage coil including a wire wound around a cylindrical winding drum of a bobbin which is provided with flanges on both ends of the winding drum; a low-voltage coil formed of a flat plate member having an open ring shape, the low-voltage and high-voltage coils being alternately laminated in their axial directions; and a cover member which has a ring plate shape and is coaxially laminated on an outside of a laminate in an axial direction. The low-voltage coil is between the high-voltage coil and the cover member, and a wall portion protruding in the axial direction from the bobbin of the high-voltage coil and a wall portion protruding in the axial direction of the cover member are alternately disposed.

Air core reactor includes a coil connected between first and second terminals. The coil is made of a succession of bundles of conductor (B1, B2, B3, . . . , BN) connected in series along an axis between the first terminal and the second terminal. Each bundle is made of one wire wound around the axis to form a multi-layer winding having a cross-section of N winding layers in a direction perpendicular to the axis, from a winding layer of rank 1 which is the closest to the axis to a winding layer of rank N which is the furthest from the axis. Each perpendicular winding layer includes several winding layers in the direction of the axis. The number of axial winding of the perpendicular winding layer of rank j (j=2, . . . , N) is equal or less than the number of axial winding layers of the perpendicular winding layer of rank j1.