Patent ID: 7847663

Claim:
DC choke arrangement of a power transformer, especially of a frequency converter, provided with a DC intermediate circuit and connected to an AC electricity network, for limiting the harmonics of the network current taken from the AC electricity network by an appliance, said DC choke arrangement comprising: at least one choke (Ldc+, Ldc−), arranged in a magnetic core, which contains pillar parts and yoke parts ( 1 a ′, 1 b ′, 2 a ′, 2 b ′), at least one permanent magnet being arranged in the magnetic core of the choke, wherein the at least one permanent magnet is positioned at an angle with respect to the longitudinal direction of the part or parts of the magnetic core such that the cross-sectional area of the at least one permanent magnet is greater than the cross-sectional area of the part of the magnetic core; wherein in the magnetic circuit the cross-sectional areas of the at least one permanent magnet and of the magnetic core are fitted such that the density of the magnetic flux at the point of the at least one permanent magnet when the thinnest section of the magnetic core saturates is lower than the magnetic flux with which the permanent magnet demagnetizes.