Abstract: There is provided a high frequency AC inverter comprising a DC-DC circuit, an output power circuit and a load circuit and a controller. The load circuit comprises a load circuit detector configured to detect the electrical parameters of the load circuit. The output power circuit comprises a DC to AC driver having a variable frequency output, a HFAC driver circuit and a transformer coupled to the HFAC driver circuit and the load circuit.

Abstract: A method of protecting a power transformer (101) in a power supply distribution grid (100) is described. The method comprises monitoring low frequency electrical signals in a circuit coupled to the power transformer (101) to provide a first detection signal (211); monitoring electromagnetic radiation to provide a second detection signal (212); in the event that the first detection signal (211) exceeds a first threshold, operating a protection switch (204a) connected to the transformer (101) to break the circuit and to reconnect the circuit in response to the first detection signal dropping below the first threshold; in the event that the second detection signal exceeds a second threshold, operating the protection switch (204a) to break the circuit at least until the first detection signal has dropped below the first threshold.

Abstract: According to the invention there is provided a HFAC power supply configured to be powered by a DC supply, the HFAC power supply comprising a power circuit, a load circuit and a controller, the power circuit and the load circuit being inductively coupled, the power circuit comprising a voltage regulator configured to output an output voltage, a DC to AC driver and a driver circuit comprising an LC resonant bridge circuit and a primary inductor inductively coupled to the load circuit.

Abstract: An inductively powered device driver comprising a secondary winding to be coupled to a primary winding and a ferrite core formed of two separable parts, and further comprising a permanent magnet attached to each part of the ferrite core. The permanent magnet(s) are preferably separated from the ferrite core by an insulator. One part of the ferrite core preferably comprises a metal plate positioned between the two parts of the ferrite core.