Cooling element for a liquid-cooled reactor or a liquid-cooled transformer and reactor or transformer with such a cooling element

摘要

With liquid-cooled chokes or transformers, high parasitic eddy current losses occur in the metallic cooling elements which are mounted between or on the magnetically conductive core and the windings, depending on the operating frequency and the magnetic flux densities. These are caused by magnetic stray fields that occur between the windings and the core - especially in the area of air gaps in the core. Thus, forcibly, the introduced cooling elements are penetrated by stray magnetic fields. The eddy current losses in the cooling elements are undesirable and can certainly account for 25% of the total power loss, depending on the construction and operating mode of the choke or of the transformer, whereby the efficiency drops very sharply. To significantly reduce the parasitic eddy current losses in the metallic cooling elements, at least on the underside 105 of a cooling element 100 below and adjacent to the channels 120 for the cooling liquid several, preferably very narrow and parallel grooves 110 are incorporated with any depth and slope, which Eddy current loops in the cooling element 100 partially interrupt and compensate. The longitudinal orientation of the grooves 110 in the cooling element 100 preferably follows the magnetic main flow direction in the legs of the throttle or the transformer. The introduced grooves 110 can then be filled with a impregnating resin 115 or other electrical insulation material 115 in order to increase the thermal conductivity against air. The optimized cooling elements in liquid-cooled reactors and transformers, which are operated with a frequency-sensitive current - in particular at a high harmonic component of the current - a significant reduction in power dissipation and increase the efficiency and continue to be widely used for certain types of inductors and transformer types largely universal.