This dataset results from the review of technical data of transformer for 135 datasheets from 3 manufacturers (Eaton, General Electric, Schneider). This dataset compiles characteristics, including mass, rated power, Transformer type, Primary and secondary voltage, number of phases, type of coil, losses, and efficiency. This research work was supported by the CDP PowerAlps, the project CIRCULAR, and EECONE, which received funding from the Chips Joint Undertaking under grant agreements 101112065 and BPI France.