1. A power electronics device, such as a frequency converter, comprising power units (REC1, INU1, INU2, CDC1), a metal frame and a DC bus arrangement in which the power units are connected, wherein the power units are assembled inside the metal frame, and wherein the shape of the metal frame is elongated with rectangular cross-sectional shape, consisting of a bottom part and from that essentially vertical oriented side wall parts, wherein the DC bus arrangement is arranged on top of the bottom part of the metal frame and separated by an insulator layer (Si) from the metal frame, and the DC bus arrangement comprises a first DC bus current conductor (DC+) and a second DC bus current conductor (DC?) which are arranged side by side and apart from each other, wherein the DC bus current conductors (DC+, DC?) have a flat shape in such a way that their thickness dimension is essentially shorter than their width dimension;and wherein the first DC bus current conductor (DC+) and the second DC bus current conductor (DC?) are only separated from the bottom part of the metal frame by a thickness of the insulator layer (Si).