US Patent 7471183 Transformer

There is provided a joint structure of a wound iron core in which iron core characteristics can be enhanced by improving the distribution of magnetic flux within an iron core. A wound iron core is formed to provide a joining structure or a butt joining structure and a lap joining structure disposed in an appropriate arrangement in which the a margin of overlapping is more increased as being closer to an outer periphery from an inner periphery of the iron core, taking a distribution of magnetic flux density within the iron core into consideration.