A coil component includes a core that includes a core part having a first end portion and a second end portion; and a first wire and a second wire that are wound around the core part from the first end portion to the second end portion in substantially helical shapes so as to have substantially the same number of turns. The first wire is wound so as to form a first layer that contacts the peripheral surface of the core part, the second wire is wound such that at least part of the second wire forms a second layer on the outside of the first layer, and a first coil length formed by the first wire is longer than a second coil length formed by the second wire.

A planar transformer including a planar first primary coil; a planar first secondary coil inductively coupled with the first primary coil; and a transformer magnetic core for guiding a magnetic flux generated by the first primary coil and/or the first secondary coil around at least a first opening of the transformer magnetic core. The first primary coil and the first secondary coil are coiled around the transformer magnetic core through the first opening. The first primary coil and the first secondary coil are arranged on a first plane. The embodiments further refer to a battery charger including such a planar transformer.

One object is to reduce, in a common mode choke coil having three coil conductors, a deviation in stray capacities generated between the coil conductors. A common mode choke coil according to one embodiment of the present invention includes a first coil conductor, a second coil conductor, and a third coil conductor. In said embodiment, the first coil conductor, the second coil conductor, and the third coil conductor extend parallel with each other in a first region in plan view as seen from an axial direction along the coil axis. In said embodiment, in the first region, when seen in a cross section cut along a plane including the coil axis, in an n-th turn, an arranging order of the first coil conductor, the second coil conductor, and the third coil conductor from an inner side in a radial direction thereof is inverted from that in an n+1th turn.

A method for suppressing magnetizing inrush current of the transformer with flux linkage control includes connecting a small-capacity direct current/alternating current (DC/AC) converter with the secondary winding or auxiliary winding of transformer, detecting the primary side phase voltage before closing load, inducing the core flux linkage reference according to the relationship between the winding voltage and core flux linkage. The core flux linkage closed-loop PI control system is constructed to control the converter voltage in the synchronous coordinate, then the core flux linkage can track its reference with no static error, thus the sinusoidal flux linkage with 90-degree difference from the grid voltage can be pre-established in the core before no-load closing. By these methods, no matter when the main transformer closes, the core flux linkage is always in the steady state, and the magnetizing inrush current can be eliminated completely.

A method for suppressing magnetizing inrush current of the transformer with flux linkage control includes connecting a small-capacity direct current/alternating current (DC/AC) converter with the secondary winding or auxiliary winding of transformer, detecting the primary side phase voltage before closing load, inducing the core flux linkage reference according to the relationship between the winding voltage and core flux linkage. The core flux linkage closed-loop PI control system is constructed to control the converter voltage in the synchronous coordinate, then the core flux linkage can track its reference with no static error, thus the sinusoidal flux linkage with 90-degree difference from the grid voltage can be pre-established in the core before no-load closing. By these methods, no matter when the main transformer closes, the core flux linkage is always in the steady state, and the magnetizing inrush current can be eliminated completely.

A coil device includes a first core, a second core, and a conductor. The first core includes a first leg. The second core is disposed with a gap between the first leg and the second core. The conductor is at least partly disposed between the first core and the second core. A notch is formed on the conductor at a position corresponding to the gap.

A power generating transformer system (PGTS) where the core of the transformer has one of the generalized configurations is presented. Also, a power factor correction method in a power generating transformer system (PGTS) and a PGTS functioning also as power supply are presented. A PGTS generates an AC voltage with the frequency which lets the desired relative phase which is the difference between the phase of the flux at the primary coil and that of the flux at the secondary coil be in a specified range. And by controlling the reactive power at the primary coil of the transformer of the transformer circuit or at the location where the AC voltage is generated, the power factor correction is done using one or more components in the transformer circuit (TC). Finally, block diagrams of PGTS are presented.

A coil device includes a core having a winding core portion and flange portions and formed in end portions of the winding core portion, a first winding portion formed by winding a first primary wire and a first secondary wire around the winding core portion, and a second winding portion formed by winding a second primary wire and a second secondary wire around the winding core portion. The second winding portion is formed with an alternating winding region where the second primary wire and the second secondary wire are alternately disposed and wound and a continuous winding region where either the second primary wire or the second secondary wire is continuously wound.

A device having a step-up transformer that includes a magnetic core, a primary winding for connecting to an AC network, and an output secondary winding; and a step-down transformer that includes a magnetic core, a primary winding identical to and connected opposite to the secondary winding of the step-up transformer, and a secondary winding identical to the primary winding of the step-up transformer. The opposite connected secondary winding of the step-up transformer and primary winding of the step-down transformer form a second voltage harmonic generation circuit that generates, when voltage is supplied to the step-up transformer from the AC network, a second voltage harmonic in the windings and magnetic cores of said transformers so that frequency of external voltage oscillations of the AC network is doubled in said second voltage harmonic generation circuit, thereby generating an autoparametric resonance therein.

A coil component includes a core that includes a core part having a first end portion and a second end portion; and a first wire and a second wire that are wound around the core part from the first end portion to the second end portion in substantially helical shapes so as to have substantially the same number of turns. The first wire is wound so as to form a first layer that contacts the peripheral surface of the core part, the second wire is wound such that at least part of the second wire forms a second layer on the outside of the first layer, and a first coil length formed by the first wire is longer than a second coil length formed by the second wire.