Abstract: Electric welding method is provided of aluminium or aluminium alloy in a magnetic field, the aluminium or aluminium alloy adjacent to a weld joint under formation has an oxide layer, and the free end of a welding wire is supplied with a surrounding shielding gas. Furthermore, a welding wire is used that comprises aluminium or aluminium alloy provided with an oxide-inhibiting coating, which forms the outer covering or sheath of the welding wire and/or that as said shielding gas there is used a shielding gas with oxygen incorporated therein, or that the shielding gas is supplied with oxygen during the welding process. When the process is carried out in a magnetic field, the minimum frequency of the welding current is selected as a function of the strength of the magnetic field. A method is also provided for producing the welding wire and necessary material conditions for a usable welding gun.

Abstract: The present invention relates to an induction heating coil comprising a litz cable which is wound into a spiral to form a bobbin, and means for cooling said cable indirectly. The litz cable is arranged to be cooled by means of an indirect cooling system that comprises a tube which is wound in an intermeshed fashion with the windings of the litz cable. The present invention relates also to a method on a paper or board machine or on a paper finishing machine, in which method at least one induction heating coil comprising a wound litz cable is used for heating a component, and said coil is cooled indirectly by a cooling medium.

Abstract: A new control strategy for IGBTs when used in high frequency (75 kHz-500 kHz) high power (10 kW-5 MW) inverters with series resonant load, a topology commonly used for induction heating. The strategy changes the IGBT strain elements into a total stress picture that fits the IGBP's behaviour and internal nature better. This makes the IGBT operate much more efficient, thus increasing the maximum output power from the inverter significantly compared to a standard control scheme. This makes the IGBT based inverter a much cheaper alternative than a MOSFET inverter, which has been state of the art for this application.