FIELD: electricity.SUBSTANCE: power transfer from fixed unit to rotating one is performed by the rotating transformer comprised of stator and rotor magnet cores of circular packs matched by bore of the stator magnet core through circular air gap with AC toroidal windings placed between neighbouring packs. The opposite sides of circular packs have closing magnet cores. In order to reduce magnetic resistance in transition from the circular pack to longitudinal one and to reduce magnetic noise the circular packs are complete with end locking rings with centring circular grooves and divided in circumferential direction into interconnected segment packs of laminated sheets aligned with closing packs thus forming W-shape with even distribution in circumferential direction and inserted into circular grooves of end locking rings.EFFECT: reduced magnetic resistance.2 dwg