Abstract: An ignition coil for internal combustion engine includes: a center core disposed on an inner side of a primary coil and a secondary coil and a side core disposed on an outer side of the primary and secondary coils whose one end face abuts on one end face of the center core and the other end face abuts on the other end face of the center core via a magnet. The side core is formed of a plurality of side core portions obtained by dividing laminated magnetic steel plates at different positions in a longitudinal direction thereof and has a superimposed portion in which the magnetic steel plates of the adjacent side core portions mutually superimpose between the different positions in the longitudinal direction. It thus becomes possible to provide an ignition coil for internal combustion engine capable of suppressing an increase of magnetic circuit resistance markedly without deteriorating assembly workability.

Abstract: A small reactor with high heat-release performance is provided. A reactor 1 includes an assembly (10) and a case (4), the assembly (10) having a coil (2) and a magnetic core (3) at which the coil (2) is arranged, the case (4) housing the assembly (10). The case (4) includes a bottom plate (40) that contacts a fixing object when the reactor (1) is installed on the fixing object, a side wall (41) that is mounted on the bottom plate (40) with an adhesive and surrounds the assembly (10), and a junction layer (42) that fixes the coil (2) to an inner surface of the bottom plate (40). The bottom plate (40) is formed of a material with higher thermal conductivity than that of the side wall (41). The reactor (1) easily transfers heat of the coil (2) to the bottom plate (40) and hence has high heat-release performance because the reactor (1) includes the bottom plate (40) with the high thermal conductivity and the coil (2) is joined to the bottom plate (40) through the junction layer (42).

Abstract: An inductor comprises a magnetic core and a coil. The magnetic core has a wound portion around which the coil is wound, and a peripheral portion. The magnetic core is formed from two or more preliminarily-formed-bodies which are pressure-molded in a state where the coil winds one or more preliminarily-formed-bodies which form the wound portion. The preliminarily-formed-bodies include at least one preliminarily-formed-body which forms the peripheral portion while not form the wound portion. Each of the preliminarily-formed-bodies is made of a mixture of flat magnetic powders and an organic binder so as to have a plate-like shape. The flat magnetic powders are oriented so as to be parallel to the preliminarily-formed-body.

Abstract: A novel coupler, coupler housing and ferrite core and associated elements and concepts thereof and therefor for use in particular with an Inductive Power Transfer or Distributed Power System.

Abstract: A transformer core is disclosed, which can include at least three hollow-cylindrical rectangular shaped core-discs wound from a magnetic band-like material, wherein two opposed limb areas and an upper and lower yoke area can be formed along a circumferential path. The core-discs can include one first and at least one second slanted area parallel to the circumferential path in the belonging limb area. The at least three core-discs can be connected according to a polygonal layout at their first slanted areas, which can be arranged adjacently face to face. Conical shaped polygonal adapter plates fitted to the polygonal layout within the upper and lower yoke areas, which can be clamped together.

Abstract: A magnetics assembly (100) including a transformer (1) made of litz wire. The transformer includes a toroid core (2) and a bundle of wires (3) winding around the toroid core. The bundle of wires includes first to eighth wires, and has a central portion with all eight wires twisted together and winding around the toroid core. First and second ends of the bundle of wires oppositely extend out from the toroidal core. The ends of the first to eighth wires are connected to form a primary and a secondary coils of the transformer, wherein the second ends of the first wire and the second wire, and the first ends of the third wire and the fourth wire are sorted out to form central taps (35, 36) of the primary and secondary coils, respectively.

Abstract: A power converting apparatus makes reduction of power loss possible and operates in a two-phase mode. A power converting apparatus of the inventive concept includes I-shaped block cores, each being made of a magnetic material; and E-shaped cores, each being produced by combining two L-shaped magnetic materials to each of the I-shaped cores. In each of the E-shaped cores, the block core is defined as a central leg, the other two legs are defined as a first outside leg and a second outside leg, respectively, and a closed magnetic path is configured by two E-shaped cores combined such that one of respective central legs in the two E-shaped cores, one of respective first outside legs therein, and one of respective second outside legs therein are caused to face the other of the central legs, the other of the first outside legs, and the other of the second outside legs.

Abstract: A multi-coil choke for an AC power conditioner includes a magnetic core having first, second and third parallel legs. A first coil wrapped around the first leg terminates in first and second leads at respective ends. A second coil wrapped around the second leg terminates in first and second leads at respective ends. A third coil wrapped around the third leg terminates in first and second leads at respective ends. A fourth coil is formed from a proximal portion of the second lead of said first coil. The fourth coil is wrapped around a distal portion of the second lead of the third coil. A fifth coil is formed from a proximal portion of the second lead of the third coil. The fifth coil is wrapped around a distal portion of the second lead of the first coil. AC power conditioners using one or more such chokes are also disclosed.

Abstract: A magnetic device including a first magnetic core is disclosed. The first magnetic core includes a base having a first edge; a first contacting structure disposed on the base; and a second contacting structure disposed on the base, wherein a distance between an inner surface of the first contacting structure and the first edge is larger than a distance between an inner surface of the second contacting structure and the first edge.

Abstract: A transformer includes a first magnetic permeable device, a primary winding wire, a secondary winding wire and a second magnetic permeable device. The primary winding wire and the secondary winding wire are wound on the first magnetic permeable device. The second magnetic permeable device includes a first flange and a second flange. The first flange is disposed at one end of the second magnetic permeable device, and the second flange is disposed at the other end of the second magnetic permeable device. The first flange and the second flange are connected to the first magnetic permeable device. The magnetic permeability of the second magnetic permeable device is larger than that of the first magnetic permeable device.

Abstract: A coupled inductor comprises an annular core 1 and coils 2a, 2b wound around the core. The annular core 1 includes a sendust core having a maximum differential permeability that is equal to or greater than 30.

Abstract: A transformer includes a core having a first leg, a second leg and a third leg, a split primary winding including first turns about the first leg electrically coupled with second turns about the third leg, and a secondary winding about the second leg. Magnetic flux linking the first turns of the split primary winding and magnetic flux linking the second turns of the primary winding link the secondary winding.

Abstract: The invention provides a system for monitoring an operational parameter of a gas turbine, including a magnetic coupling between a signal source and a data output terminal. The magnetic coupling comprises a primary coil electrically connected to the signal source and wound around a first magnetic core section, and a secondary coil electrically connected to the output terminal but electrically isolated from the primary coil and wound around a second magnetic core section, wherein the first and second magnetic core sections are physically separated from one another.

Abstract: Methods and structures for constructing a magnetic core of a coupled inductor. The method provides for constructing N-phase coupled inductors as both single and scalable magnetic structures, where N is an integer greater than 1. The method additionally describes how such a construction of the magnetic core may enhance the benefits of using the scalable N-phase coupled inductor. The first and second magnetic cores may be formed into shapes that, when coupled together, may form a single scalable magnetic core. For example, the cores can be fashioned into shapes such as a U, an I, an H, a ring, a rectangle, and a comb, that cooperatively form the single magnetic core.

Abstract: The invention relates to a differential mode and common mode choke comprising: a ferromagnetic core comprising three branches (1, 2, 3) extending between a bottom part (5) and a top part (4), a first coil (b1) wound around the first lateral branch (1), a second coil (b3) wound around the second lateral branch (3), the first lateral branch (1) being separated from the top part (4) by a first air gap (e1) and from the bottom part (5) by a second air gap (e10), the second lateral branch (3) being separated from the top part (4) by a first air gap (e3) and from the bottom part (5) by a second air gap (e30), the central branch (2) being separated from the top part (4) by a first air gap (e2) and from the bottom part (5) by a second air gap (e20).

Abstract: According to an embodiment, there is provided a resonator including: a first magnetic material core, a first winding and a first protruding portion. The first magnetic material core includes at least one first core block of magnetic material. The first winding is wound around the first magnetic material core. The first protruding portion is formed so as to protrude from a part of the core block between a first end of the core block and the first winding.

Abstract: An inductive component having a printed circuit board (“PCB”) with a first side and a second side. An aperture extends through the PCB and a conductive winding is printed onto the PCB surrounding the aperture. A core is formed by a first core member and a second core member. The first core member includes a first base member with at least one joining surface which is solderable to the first side. A first core leg extends at least partially through the aperture. The second core member includes at least a second base member and is coupled to the first core member or the second side. To manufacture the PCB, the first core member is soldered to the first side and then the PCB is inverted. The second core member is then coupled to at least one of the first core member or the second side.

Abstract: There is provided a coil component capable of minimizing mutual interference while disposing a plurality of coil parts in a single component. According to an embodiment of the present invention, the coil component includes: a bobbin part including two body parts disposed in parallel, the two body parts having coils wound therearound; and a core including two inner legs inserted into the body parts and two outer legs disposed outwardly of the body parts, the inner legs and the outer legs having the same cross sectional area.

Abstract: An M phase coupled inductor includes a magnetic core including a first end magnetic element, a second end magnetic element, and M legs disposed between and connecting the first and second end magnetic elements. M is an integer greater than one. The coupled inductor further includes M windings, where each winding has a substantially rectangular cross section. Each one of the M windings is at least partially wound about a respective leg.

Abstract: A power module includes a metal housing formed of a metal case and a metal cover plate, a transformer module accommodated in the metal housing, including a base member having an iron core holder block suspending in a center opening thereof and two connection blocks disposed at two opposite sides thereof, metal conducting terminals arranged in two sets and respectively mounted in the connection blocks of the base member, a winding wound round the iron core holder block, two iron cores respectively attached to opposing top and bottom sides of the iron core holder block and two circuit boards respectively inserted into the two connection blocks of the base member and electrically coupled with two opposing connection terminals of the winding and respective vertical contact ends of the metal conducting terminals, and a thermo-conductive insulating glue filled in the metal housing to package the transformer module.

Abstract: An M phase coupled inductor includes a magnetic core including a first end magnetic element, a second end magnetic element, and M legs disposed between and connecting the first and second end magnetic elements. M is an integer greater than one. The coupled inductor further includes M windings, where each winding has a substantially rectangular cross section. Each one of the M windings is at least partially wound about a respective leg.

Abstract: A building-block-combined-type high power transformer includes a first iron core body , a second iron core body , a plurality of plate bodies, and a plurality of isolating bodies. The first iron core body and the second iron core body have a first side wing part and a second side wing part respectively at both sides thereof. Both of the first side wing part and the second side wing part being a circular shape at both ends respectively thereof have a first open channel and a second open channel formed between thereof where the second iron core body is in contact with the first iron core body. Each of the plate bodies being positioned in both the first open channel and second open channel has an open hole, for containing both of the first side wing part, and the second side wing part, and a guided channel that is positioned on the second side of the open hole.

Abstract: A coil structure according to one embodiment of the present invention includes, but is not limited to: a plurality of core members having impedances with different frequency characteristics; and a winding wire member wound around the plurality of core members.

Abstract: The instant disclosure relates to a low-profile transformer. The transformer in accordance with the present invention comprises a core unit having a pair of opposingly arranged base portions, an inserting portion, and at least a primary coil and a secondary coil wound around the inserting portion. The top-facing edge of the lateral portions is chamfered to enable tighter fitment into a receiving housing, such as a light tube. The transformer may also include a frame unit having a rounded flange that conforms to the shape of the wound coil. The instant disclosure further introduces a method for providing a low-profile transformer that is particularly suitable for adapting in a tubular light device. The physical features and dimension of the transformer may be determined by methods that utilize the analysis of a characteristic equation in accordance with specific operating requirements.

Abstract: A vibration-suppressed transformer is fixed to a base plate and includes a magnetic lower core, two or more magnetic upper cores, primary and secondary coils. The lower core is on the base plate. The upper cores are arranged face to face over the lower core. The coils are arranged between the lower and upper cores. Each upper core contacts the lower core, on an outer side of the coils, with a first gap being provided between the upper and lower cores, on an inner side of the coils. The upper cores are extended towards each other from the outer to the inner side of the coils, with a second gap being provided therebetween. The second gap is provided therein with a non-magnetic pressing member to press the lower core against the base plate, on an inner side of the coils.

Abstract: A coil device 10 comprises a first bobbin 40 having a first bobbin plate 42 provided with a first hollow cylinder 44 on which a primary coil 20 is wound at the outer periphery, and a second bobbin 50 mounted on the first bobbin 40 and having a second bobbin plate 52 provided with a second hollow cylinder 54 on which a secondary coil 30 is wound at the outer periphery. A winding center C1 of the primary coil 20 and a winding center C2 of the secondary coil 30 displace with a predetermined displacement (Lx) along a predetermined reference direction X.

Abstract: A multi-coil choke for an AC power conditioner includes a magnetic core having first, second and third parallel legs. A first coil wrapped around the first leg terminates in first and second leads at respective ends. A second coil wrapped around the second leg terminates in first and second leads at respective ends. A third coil wrapped around the third leg terminates in first and second leads at respective ends. A fourth coil is formed from a proximal portion of the second lead of said first coil. The fourth coil is wrapped around a distal portion of the second lead of the third coil. A fifth coil is formed from a proximal portion of the second lead of the third coil. The fifth coil is wrapped around a distal portion of the second lead of the first coil. AC power conditioners using one or more such chokes are also disclosed.

Abstract: Provided is a reactor which uses a reactor core in which J-shaped iron cores are oppositely disposed in a ring shape. In the ring shape, an axial outer circumferential part of a first coil wound around a first gap and an axial outer circumferential part of a second coil wound around a second gap overlap each other in an axial direction. Regarding four holding stay parts disposed at four corners of the reactor, the rigidity of the holding stay parts close to the first gap and the second gap is lower than the rigidity of the holding stay parts far from the first gap and the second gap.

Abstract: A coil device 10 comprises a bobbin 40 having a bobbin plate 42 provided with a first hollow cylinder 44 on which a primary coil 20 is wound, and a case 50 provided with a second hollow cylinder 54 wound by a secondary coil 30 at the outer circumference. On the bobbin plate 42, a primary terminal 70 connecting to the primary coil 20 and a secondary terminal 72 connecting to the secondary coil 30 are formed, and a tip end portion 55a of case 50 is extended to the end portion of the bobbin plate 42 to which the secondary terminal 72 is formed. Further, on the tip end portion 55a, plural first grooves 57a for lead are formed.

Abstract: A cost effective solution for construction of high frequency, double ended, isolated, push pull, center tapped power transformers operating in continuous/discontinuous mode with minimized winding proximity losses comprises at least two identical sets of windings with identical coupling coefficients. Each set of windings consists of at least one primary winding and at least one secondary winding tightly coupled to each other. Both the sets of windings are loosely coupled to each other with a magnetic field isolating separator.

Abstract: A controllable inductor system includes a multiphase inductor comprising a central winding, a first control winding, and a second control winding, and a control portion comprising a first control logic portion operative to receive a signal indicative of a current of the first control winding and a signal indicative of a current of the sum of the first control winding and the second control winding and modulate a first pulse width modulated signal to responsively control a first transistor connected to the first control winding, and a second control logic portion operative to receive the signal indicative of the current of the first control winding and a signal indicative of a current of the sum of the first control winding and the second control winding and modulate a second pulse width modulated signal to responsively control a second transistor connected to the second control winding.

Abstract: A high-frequency transformer includes a plurality of cores having a central leg, the cores being arranged to form core windows that are separated by the central legs. A primary winding has a predetermined length of electrically conductive wire that is wound about the central legs and extends through each of the core windows. One or more secondary windings extend through each core window, generally adjacent to the primary winding. The core windows are sized and shaped to provide a predetermined amount of leakage inductance between the primary and secondary windings, and are further adapted to provide a path for cooling air through an interior portion of the transformer.

Abstract: Power inductor has a magnetically isotropic core including two or more laminations. At least a first lamination can include anisotropic magnetic material having a first orientation of magnetic anisotropy. At least a second lamination can include anisotropic magnetic material having a second orientation of magnetic anisotropy, the second orientation being different than the first orientation.

Abstract: A reactor having a good heat dissipation effect is provided. The reactor includes one coil formed by winding a wire, a magnetic core arranged inside and outside the coil and forming a closed magnetic circuit, and a case for housing an assembly of the coil and the magnetic core. An end surface of the coil has a race track shape, and the coil is housed in the case such that the axial direction of the coil is parallel to an outer bottom surface of the case. A part of an outer peripheral surface of the coil is covered with the magnetic core (outer core portion), and a remaining part thereof not covered with the magnetic core is contacted with an inner bottom surface of the case. Since a part (mainly a linear portion) of the outer peripheral surface of the coil is directly contacted with the inner bottom surface of the case, heat of the coil can be directly dissipated such that the heat is released through the case to an installation target, e.g., a water cooling base, on which the case is installed.

Abstract: A reactor 1A of the present invention includes a sleeve-like coil 2, a magnetic core 3A having an inner core portion 31 disposed inside the coil 2 and an outer core portion 32A disposed outside the coil 2 to form a closed magnetic path with the inner core portion 31. The outer core portion 32A is a mold product (a hardened mold product) of a mixture of magnetic powder and resin, and structured by a combination of two radially divided pieces 321 and 322 that can be separated in the radial direction of the coil 2. Since the outer core portion 32A is structured by a plurality of divided pieces, the manufacturing time per divided piece can be shortened and excellent productivity of the reactor 1A is exhibited. When the hardened mold product is formed by injection molding, further excellent productivity is exhibited. Since the seam portion of the radially divided pieces 321 and 322 does not break the magnetic flux, no gaps that divide the magnetic flux occur between the divided pieces 321 and 322.

Abstract: There are provided a coil component capable of easily mounting in a narrow mounting space, and a display device including the same. The coil component including: a bobbin including a cylindrical body part having a plurality of coils wound on an outer peripheral surface thereof, flange parts formed at both ends of the body part, and at least one or more core support parts protruded from outer surfaces of the flange parts; and a core coupled to the bobbin and seated on and fixed to the core support part.

Abstract: A reactor comprises a reactor core in which two U-shaped core members are connected in a ring shape with gap sections including adhesive layers therebetween, a primary insert-molded resin part which is provided covering leg parts of the core member and which includes joint sections formed around end surfaces of the leg parts a coil placed around the gap sections and the leg parts of the core members, and a secondary insert-molded resin part which is made of a thermoplastic resin and which is insert-molded around the coil to fix the coil on the reactor core and fix the leg parts of the two core members in a connected state, wherein the joint sections of the primary insert-molded resin parts are fitted to each other in a state where the core members are placed connected in a ring shape, to form a peripheral wall surrounding the gap section.

Abstract: A transformer includes a winding member, a magnetic core assembly and an insulating seat. The winding member includes a bobbin, a primary coil and a secondary coil. The primary coil and the secondary coil are wound on the bobbin. The magnetic core assembly includes a first magnetic core and a second magnetic core. The winding member is arranged between the first magnetic core and the second magnetic core. The insulating seat includes a receptacle, at least one ventilation hole, at least one sheltering member and plural pins. The winding member and the magnetic core assembly are accommodated within the receptacle. The ventilation hole is formed in the sheltering member. The first terminals of the primary coil and/or the second terminals of the secondary coil are connected with the pins.

Abstract: A magnetic element may include a first core member, a second core member facing the first core member along an entire outer periphery thereof, a coil, and a base shaped body on which the first core member and the second core member are placed. The base shaped body is provided with a base member and a terminal member, and the terminal member is provided with a binding terminal part, which projects outward in a first corner part of the base member and projects from the base member on a side lower than a portion of a winding frame part side of one flange part. The second core member is provided with a cutout part at a portion corresponding to the first corner part of the base member for allowing insertion of an end drawn out from the winding frame part in a state of not contacting the second core member.

Abstract: The disclosure provides a magnetic core comprising a base, a center column, a first side column and a second side column fixed to the base. The first side column, the second side column and the center column are defined an annular space for accommodating a bobbin and/or a winding. The annular space have a first core opening and a second core opening thereon. A size of the first core opening between the first side column and the second side column is defined as a first core opening width. A size of the second core opening between the first side column and the second side column is defined as a second core opening width. Wherein at least one wire receiving space is provided at the base of the magnetic core, and the wire receiving space is located within the first core opening and/or the second core opening.

Abstract: Divided cores 11, 12 includes left and right leg portions and a yoke portion and formed by molding a yoke portion side core material within resin. The leg portions of the divided core are formed by tubular core mounting portions 41, 42. I-shaped leg portion side core materials 51-53 and spacers 6 are mounted in the tubular core mounting portions. A ring-shaped molded core 1 is formed by abutting and integrating the respective leg portions of two divided cores, and a coil 100 is wound around the molded core.

Abstract: Provided is a reactor and a reactor component that can prevent cracking of a resin portion that is interposed between a coil and an internal core portion. The reactor includes a coil 10 and a core that includes an internal core portion 22 and a couple core portion 24. The coil 10 is formed by helically winding a wire. The internal core portion 22 is disposed inside the coil and forms a part of a closed magnetic path. The couple core portion 24 is joined to the internal core portion 22 and forms the remaining part of the closed magnetic path. The reactor includes a resin portion (internal resin portion 30) including a region that is interposed between the coil 10 and the internal core portion 22, and a cushioning member 70 that is interposed between the resin portion and the internal core portion 22 and that does not cover the couple core portion 24. It is preferable that the material of the cushioning member 70 has a Young's modulus that is smaller than a resin material of the resin portion.

Abstract: A current transformer supplying a power for an electronic controller comprises two independent core magnetic circuits, wherein a first core magnetic circuit is a closed loop formed by connecting a U-shaped core and a linear core, a primary conductor extends through the closed loop, and a secondary winding for power supply is wound on the linear core; a second core magnetic circuit having an opening shape is disposed in parallel to the linear core of the first core magnetic circuit, and the open end of the second core magnetic circuit is coupled to the first core magnetic circuit through air gaps. The area of the cross section of the linear core is less than that of the cross section of the U-shaped core, so that the linear core can be magnetically saturated earlier than the U-shaped core. The centerline length of the U-shaped core is 1.5 to 4 times of that of the linear core.

Abstract: A magnetic device includes a T-shaped magnetic core, a wire coil and a magnetic body. The T-shaped magnetic core includes a base and a pillar, and is made of an annealed soft magnetic metal material, a core loss PCL (mW/cm3) of the T-shaped magnetic core satisfying: 0.64×f0.95×Bm2.20?PCL?7.26×f1.41×Bm1.08, where f (kHz) represents a frequency of a magnetic field applied to the T-shaped magnetic core, and Bm (kGauss) represents the operating magnetic flux density of the magnetic field at the frequency. The magnetic body fully covers the pillar, any part of the base that is located above the bottom surface of the base, and any part of the wire coil that is located directly above the top surface of the base.

Abstract: A magnetic core includes a first core having a recess and a second core, which has a first end portion and a second end portion both held in contact with the first core and forms a closed magnetic path with the first core. The second core is formed of material having a lower magnetic permeability and a higher saturation magnetic flux density than those of the first core. The second end portion includes a distal surface having an area larger than the cross-sectional area of the first end portion in a direction perpendicular to the direction in which a magnetic flux flows in the closed magnetic path. The distal surface of the second end portion is held in contact with the first core and the first end portion is engaged with the recess in the first core.

Abstract: According to one embodiment, there is provided a first magnetic core, a coil and a second magnetic core. The first magnetic core includes a first magnetic core including a plurality of first core portions which are arranged with a gap to each other. The coil is wound around the first magnetic core. The second magnetic core includes at least a second core portion which is arranged in the gap between the first core portions or arranged so as to face the gap. A magnetic reluctance of the first magnetic core is lower than a magnetic reluctance of the second magnetic core.

Abstract: A thin film inductor having yokes, one or more of which is laminated, and one or more conductors passing between the yokes. The laminated yoke or yokes help reduce eddy currents and/or hysteresis losses.

Abstract: A vibration-suppressed transformer is fixed to a base plate and includes a magnetic lower core, two or more magnetic upper cores, primary and secondary coils. The lower core is on the base plate. The upper cores are arranged face to face over the lower core. The coils are arranged between the lower and upper cores. Each upper core contacts the lower core, on an outer side of the coils, with a first gap being provided between the upper and lower cores, on an inner side of the coils. The upper cores are extended towards each other from the outer to the inner side of the coils, with a second gap being provided therebetween. The second gap is provided therein with a non-magnetic pressing member to press the lower core against the base plate, on an inner side of the coils.

Abstract: The instant disclosure relates to a low-profile transformer. The transformer in accordance with the present invention comprises a core unit having a pair of opposingly arranged base portions, an inserting portion, and at least a primary coil and a secondary coil wound around the inserting portion. The top-facing edge of the lateral portions is chamfered to enable tighter fitment into a receiving housing, such as a light tube. The transformer may also include a frame unit having a rounded flange that conforms to the shape of the wound coil. The instant disclosure further introduces a method for providing a low-profile transformer that is particularly suitable for adapting in a tubular light device. The physical features and dimension of the transformer may be determined by methods that utilize the analysis of a characteristic equation in accordance with specific operating requirements.

Abstract: In a transformer core and transformer, a wound transformer core is formed from magnetic steel strips that are wound into multiple rings of different widths and arranged to define a ring-like structure having a stepped, substantially circular cross-section without any cuts or gaps in the magnetic path, or the core is wound from one or more tapered strips that are wound to define a cross-section that is circular, oval, egg-shaped, or square-shaped with truncated corners.