When winding a transformer core with resin tape, oval transformer legs can potentially cause a drop in tension. The tension of the tape, however, is highly significant. In order that the sheets in the transformer do not move a millimetre in the vertical direction during winding, a brake system with gas springs of the type GS-19-150-EE is used. Thanks to its 150 mm travel distance serving as a reserve, the tape tension is kept constant, even in the event of interruptions caused, for example, by almost right-angled cross-sections. This ensures that the winding of the transformer core, which can weigh up to several 100 metric tonnes, is uniform and even.