Patent ID: 8854168

Claim:
Power swivel ( 2 , 30 ) for the transmission of electrical power from a first terminal ( 23 , 35 , 36 ) to a second terminal ( 28 , 47 , 48 ), the swivel comprising a central part with a hub ( 31 ) and an outer ring ( 32 ) of a magnetic material, coaxial with the hub and surrounding the hub, the outer ring and the central part being rotatable relative to one another around a vertical axis ( 44 ), at least two radial arms ( 33 , 34 ) of a magnetic material projecting from the hub or from the outer ring, adjacent arms being spaced-apart, each arm carrying a conductor ( 45 , 46 ) wound around the arm to form a coil adapted for generating a magnetic flux along a radial flux path through the arm, the conductors being connected to the first terminal ( 35 , 35 ′), wherein the outer ring or the hub has a cylindrical surface ( 36 ) at close proximity to free ends of the arms ( 33 , 34 ), a plurality of axially extending conductors ( 37 ) being distributed along the circumference of the outer ring ( 32 )or hub ( 31 ) at or near the cylindrical surface ( 32 ) such that a number of axial conductors is each time situated between two adjacent radial arms, pairs of axial conductors forming coils situated along the cylindrical surface adapted for generating a magnetic flux along a magnetic flux path extending in a circumferential direction through the outer ring or hub, a closed contour ( 56 ) being formed extending radially outwardly from a first radial arm (B 4 ), into the outer ring, via the outer ring to the adjacent radial arm (B 1 ) and radially inwardly along said adjacent arm (B 2 ) and via the hub back to the first arm (B 3 ).