s longitudinal direction the pressure is not created 34 on site 34 solely in the axial area of the secondary air gap 11 it must therefore be mechanically transmitted via the magnetic shells 6 and 7 and a bearing bridge which fills the secondary air gap 11 from the pole surfaces 9 and 10 to this axial area of the working gap 13 the exciting winding 3 is arranged symmetrically to the annular secondary air gap 11 in this area i e in the axial center of the rollers 1 and 2 where it surrounds the core 4 cylindrically between two flange shaped magnet legs 5 this arrangement of the exciting winding permits a symmetrical construction of the magnetic field in the roller arrangement and an even distribution of the magnetic flux to the individual components the magnetic flux of the magnetic circuit is produced with the electrical current in the exciting winding the magnetic electromotive force is thereby created which drives the flux on its path through the magnetic circuit and is consumed as circulation voltage due to the high permeability of the magnetic material the circulation voltage decreases only on those sections of the path which pass through the air gap as a result constant magnetic potentials of varying intensity form on the opposing boundary surfaces of the air gap therefore the magnetic field intensity remains constant along an air gap the magnetic flux must always distribute evenly along air gaps for this reason the flux distribution in the magnetic circuit.