Abstract: An AC line filter in which a pair of windings are wound in an opposite dition to each other and are provided at opposing locations on a main core that forms a closed magnetic path. At least one auxiliary core which forms a shorter magnetic path than the main core is positioned adjacent the main core. The auxiliary core has at low frequency region an effective permeability higher than that of the main core. A portion of each of the pair of windings being provided in such a way that the portion is a concentrated winding which surrounds both the main core and the auxiliary core simultaneously.

Abstract: An ac line filter comprises two main cores, at least one auxiliary core disposed between the two main cores, and a pair of windings provided on the main and the auxiliary core. The main cores form shell type closed magnetic paths and enclose the auxiliary core, which forms a closed magnetic path, when the two main cores are placed one over the other. Each of the windings is wound in a concentrated manner to surround both the inner core of the main core and the auxiliary core at a location where the auxiliary core is positioned beside the main core, and is wound in a spaced manner around the inner core of the main core at a location where the auxiliary core is not positioned adjacent the main core. Each winding is divided at the center thereof and the divided ends of one winding are cross-connected with the similar divided ends of the other winding.