A system for determining an operational state of an atmospheric pressure plasma. The system has a transformer for coupling power into the atmospheric pressure plasma, a current sampling circuit configured to sample at least one current pulse flowing through a primary winding of the transformer, and a programmed microprocessor configured to determine, from a waveform of the current pulse, the operational state of the atmospheric pressure plasma. The operational state is one of: a no plasma state, a plasma origination state indicative of an ignited arc expanding into a plasma by gas flow thereinto, and a plasma maintenance state indicative of the plasma being expanded.

Radio frequency (RF) filters configured to filter undesired signal components (e.g., noise and harmonics) from RF signals are disclosed. In one embodiment, an RF filter includes a first inductor coil having a first winding and a second inductor coil having a second winding and a third winding. The second winding of the second inductor coil is configured to have a first mutual magnetic coupling with the first winding, while the third winding of the second inductor coil is configured to have a second mutual magnetic coupling with the first winding. The second winding is connected to the third winding such that the first mutual magnetic coupling and the second mutual magnetic coupling are in opposition. In this manner, the first inductor coil and the second inductor coil may be provided in a compact arrangement while providing weak mutual magnetic coupling between the first inductor coil and the second inductor coil.

Methods and apparatus for flux cancellation includes first and second inductors, wherein the first inductor is configured for coupling to a first energy source and the second inductor is configured for coupling to a second energy source. A layer of magnetic material is disposed between the first and second inductors, wherein the first and second inductors are configured such that, when driven with an oscillating current, magnetic flux generated by the first inductor is substantially canceled by magnetic flux generated by the second inductor in the layer of magnetic material.

A device for limiting a fault current for a generator, in particular of a wind turbine is provided. A first frame is made of a ferromagnetic material, wherein the first frame comprises a first frame section and a further first frame section, wherein a first gap is formed between the first frame section and the further first frame section. A first coil is wound around the first frame section, wherein the first coil is connectable to a first stator winding of a stator of the generator. A further first coil is wound around the further first frame section, wherein the further first coil is connectable to an electronic device. A first permanent magnet element is arranged inside the first gap. The first frame section and the further first frame section are formed with respect to each other such that an electromagnetic interaction between the first coil and the first permanent magnet element and the further first coil and the first permanent magnet element is provided.

Methods and apparatus for flux cancellation includes first and second inductors, wherein the first inductor is configured for coupling to a first energy source and the second inductor is configured for coupling to a second energy source. A layer of magnetic material is disposed between the first and second inductors, wherein the first and second inductors are configured such that, when driven with an oscillating current, magnetic flux generated by the first inductor is substantially canceled by magnetic flux generated by the second inductor in the layer of magnetic material.

A three phase transformer apparatus for a three phase electrical power transformation system is provided. For each phase of the three phase transformer apparatus the three phase transformer apparatus comprises: an upper core limb having a first end and a second end, a lower core limb having a third end and a fourth end, a first coil assembly comprising a first primary coil and a first secondary coil, and a second coil assembly comprising a second secondary coil and a control coil. The first primary coil and the first secondary coil of each first coil assembly are wound concentrically around the upper core limb or the lower core limb of the respective phase. The second secondary coil and the control coil of each second coil assembly are wound concentrically around the other of the upper core limb and the lower core limb of the respective phase. The second secondary coil of each second coil assembly is connected in series to the first secondary coil of the first coil assembly of the respective phase. The three phase transformer apparatus further comprises a first yoke portion connected between each of the first ends of the upper core limbs, a second yoke portion connected between each of the fourth ends of the lower core limbs, and at least one transfer yoke portion, configured to allow magnetic flux to flow between the first end of each upper core limb and the second end of the respective upper core limb, and to allow magnetic flux to flow between the third end of each lower core limb and the fourth end of the respective lower core limb. A controller is connected to the control coil of each phase and configured to apply a voltage or current waveform to the control coil in order to influence the transfer of energy between the first primary coils and the first and second secondary coils of the three phase transformer apparatus.

The present disclosure relates to a circuit for suppressing unwanted magnetic interference. The circuit can have a transformer having a first coil, a first pair of input terminals, and a first pair of output terminals. The transformer can produce a first magnetic field. The circuit can also have a harmonic trap. The harmonic trap can have a second coil and a second pair of input terminals operably coupled to the first pair of input terminals. The harmonic trap can produce a second magnetic field opposing the first magnetic field. The harmonic trap can suppress electrical signals of at least one of the first input terminals and the first output terminals of the transformer at a resonant frequency of the harmonic trap. The harmonic trap can also suppress the first magnetic field in a far field.

The disclosure provides a communication circuit including an amplification circuit, a replicator circuit, and a correction circuit. Specifically, the amplification circuit generates an amplified signal. The replicator circuit emulates the amplification circuit and generates a replicated signal that approximates the amplified signal. The replicated signal is used by the correction circuit to generate control signals for controlling the amplification circuit.

A transformer assembly comprises at least one transformer having a core. A primary winding is positioned on a first portion, a secondary winding is positioned on a second portion of the core. A neutral winding may be positioned on a third portion of the core. The secondary winding may receive an induced flux produced by an earth surface potential (ESP) via a system ground and/or receive an induced zero sequence flux produced by a non-linear load. The neutral winding may be configured to provide a mitigating flux to the secondary winding. The transformer may also be used as a filter for either GIC or triplen harmonic mitigation. In this case, the primary windings receive the zero sequence current (GIC or triplen harmonics) and the flux may be cancelled in neutral winding such that the zero sequence currents circulate between the zero sequence source and the filter transformer.

The present disclosure relates to a circuit for suppressing unwanted magnetic interference. The circuit can have a transformer having a first coil, a first pair of input terminals, and a first pair of output terminals. The transformer can produce a first magnetic field. The circuit can also have a harmonic trap. The harmonic trap can have a second coil and a second pair of input terminals operably coupled to the first pair of input terminals. The harmonic trap can produce a second magnetic field opposing the first magnetic field. The harmonic trap can suppress electrical signals of at least one of the first input terminals and the first output terminals of the transformer at a resonant frequency of the harmonic trap. The harmonic trap can also suppress the first magnetic field in a far field.