Unique systems, methods, techniques and apparatuses for a ZVT ZCT resonant converter with a variable resonant tank are disclosed. One exemplary embodiment is a system comprising a bidirectional resonant converter comprising an input/output terminal, a switching device coupled with the input/output terminal, a resonant circuit coupled with the switching device and including a variable inductor, an output/input terminal coupled with the resonant circuit, and a DC biasing circuit operatively coupled with the variable inductor. The variable inductor comprises a toroidal core, a first winding wound around the toroidal core and coupled with the switching device and the output/input terminal, a second core structured to overlap a portion of the toroidal core, and a second winding wound around the second core and coupled with the DC biasing circuit. The DC biasing circuit is controllable to vary the inductance of the variable inductor by saturating a portion of the toroidal core.

A circuit arrangement for reducing unidirectional flux component in a transformer core includes a compensation winding magnetically coupled to the transformer core, a transductor series connected with the compensation winding in a compensation current path, wherein the compensation current path has two parallel branches each containing a power winding of the transductor and an uncontrolled valve connected in series, where flow directions of the valves run counter to one another, and where each power winding is magnetically coupled to a control winding via a saturable transductor core, and includes a controller to which a detector supplies magnitude and direction information of the unidirectional flux component, and which generates a control variable supplied to each control winding such that the saturation state of the transductor core is variable such that a compensation current is formed in the compensation current path that counteracts the unidirectional flux component in the transformer core.

A circuit arrangement for reducing a magnetic unidirectional flux component in a core of a transformer includes a measuring device that provides a sensor signal corresponding to the magnetic unidirectional flux component, a compensation coil magnetically coupled to the core of the transformer, and a semiconductor switching device which is electrically arranged in a current path in series with the compensation coil to feed a current into the compensation coil, such that current is directed opposite the unidirectional flux component, where the semiconductor switching device is controlled via a control signal provided by a controller, and includes an inductive voltage divider having a first impedance component arranged in a current circuit in series with the compensation coil and the semiconductor switching device and a second impedance component arranged in parallel with the semiconductor switching device, where the first impedance component is connected in parallel with a parallel resonant circuit.

An apparatus for reducing a magnetic unidirectional flux component in the core of a transformer with at least three legs, in particular a three-phase transformer having at least one compensation winding per transformer leg, wherein the compensation windings are magnetically coupled to the core of the transformer, where two compensation windings are provided per leg, the first compensation windings of a leg are each electrically connected together in a first delta connection, in each case the second compensation windings of a leg are each electrically connected together in a second delta connection, the compensation windings of at least one leg have different numbers of windings, and where at least one switching unit is arranged in series with the compensation windings for phase angle control.

A circuit arrangement for reducing unidirectional flux component in a transformer core includes a compensation winding magnetically coupled to the transformer core, a transductor series connected with the compensation winding in a compensation current path, wherein the compensation current path has two parallel branches each containing a power winding of the transductor and an uncontrolled valve connected in series, where flow directions of the valves run counter to one another, and where each power winding is magnetically coupled to a control winding via a saturatable transductor core, and includes a controller to which a detector supplies magnitude and direction information of the unidirectional flux component, and which generates a control variable supplied to each control winding such that the saturation state of the transductor core is variable such that a compensation current is formed in the compensation current path that counteracts the unidirectional flux component in the transformer core.

A reconfigurable coupled inductor is disclosed. In one embodiment, the reconfigurable coupled inductor comprises metal rings and switches coupled to the metal rings to control at least one inductor property (e.g., coupling coefficient) based on a closed (e.g., on) or open state (e.g., off) of each switch.

A coil component has a core part 10 composing a closed magnetic path through which a closed loop of a magnetic flux passes, the magnetic flux being generated by two coils 14A, 14B that are arranged in parallel, and generate a magnetic field, and the core part 10 has a pair of I-type base cores 11A, 11B facing each other, and a pair of coupling core parts 11C, 11D. The coupling core parts 11C, 11D are each formed by linearly aligning three unit coupling cores 12A to 12F, and each of these cores 12A to 12F is formed into a configuration in which a column-shaped projection is provided on a core body, and a two-stage gap including a small gap and a large gap is to be formed mutually in a space in the adjacent unit cores 11A, 11B, and 12A to 12F by the configuration.

A fault current limiter of the type having at least one elongated core biased magnetically towards saturation by means of a surrounding magnetic field, and an AC coil surrounding the core, the fault current limiter including: an elongated core having a variable cross section along the axis of the core in the vicinity of the AC coil, providing increased saturation of the core and enhanced fault current limiting for a lower DC bias.

A device for reactive power compensation in a high voltage network having at least one phase conductor, includes a high voltage connection for each phase conductor, first and second core sections of a closed magnet circuit, a first high voltage winding enclosing the first core section, a second high voltage winding enclosing the second core section and being connected parallel to the first high voltage winding, at least one saturation switching branch being configured to saturate at least one core section has controllable power semiconductor switches, and a control unit controls the power semiconductor switches for each high voltage connection. In order to avoid leakage field losses, at least one high voltage winding has a central connection and is connected at its winding ends to the saturation switching branch. The central connection is connected to the high voltage connection.