Laminated core for a magnetic bearing having individual laminations with at least one physical interruption and method for constructing such a laminated core
The core of a combined radial-axial magnetic bearing is stacked with coated laminations each equipped with at least one radial cut ( 9 ). These cuts ( 9 ) prevent the induction of circulating currents caused by varying axial control fluxes through the central hole of the lamination stack. Magnetic symmetry is preserved by rotating every lamination with respect to the previous one.
1. A laminated core of a stator or a rotor of a permanent magnet biased or current biased combined radial-axial magnetic bearing, comprising:
a solid stack of flat soft-magnetic individual laminations;
each of said individual laminations comprising a single substantially circular structure and a single physical interruption in the single substantially circular structure, wherein said single physical interruption physically interrupts circulating currents in the plane of the individual lamination;
wherein said solid stack of flat-soft-magnetic individual laminations forms a cylindrical structure, wherein said cylindrical structure is configured in a way so as to create magnetic symmetry in the solid stack;
said single physical interruption being filled with an electrically insulating material;
said single physical interruption in adjacent laminations being rotated with respect to each other in a way such that the single physical interruption of each individual lamination is evenly distributed over a circumference of the solid stack; or
said solid stack comprising a plurality of substacks in which said single physical interruption in all adjacent laminations in a substack coincide and wherein said single physical interruption of said substacks are rotated with respect to each substack in a way such that the single physical interruption of said substacks is evenly distributed over a circumference of the solid stack.
2. The laminated core according to claim 1 , wherein none of said individual laminations are in electric contact with each other.
3. The laminated core according to claim 1 , wherein said single physical interruption is straight and radially-oriented.
4. The laminated core according to claim 1 , wherein said single physical interruption is straight and not radially-oriented.
5. The laminated core according to claim 1 , wherein said single physical interruption is shaped in the form of a dovetail-connection.
6. The laminated core according to claim 1 , wherein a cross section of said solid stack reveals no magnetic poles.
7. The laminated core according to claim 1 , wherein a cross section of said solid stack reveals more than one lamination.
8. The laminated core according to claim 1 , wherein said single physical interruption is provided on a symmetry axis of the individual lamination.
9. The laminated core according to claim 1 , wherein said single physical interruption is provided in a way such that said single physical interruption does not coincide with a symmetry axis of the individual lamination.
10. A rotating machine comprising a magnetic bearing according to claim 1 , wherein a magnetic field can always find a low-reluctant path in the vicinity of a cut, via an adjacent substack.
11. A method for constructing a laminated core for a stator or a rotor of a combined radial-axial magnetic bearing, comprising the steps:
providing a set of flat soft-magnetic laminations, wherein each of said laminations comprises a single substantially circular structure;
arranging a first soft-magnetic layer in such a way that a single physical interruption for induced circulating currents is obtained, wherein said single physical interruption in provided in the single substantially circular structure of each lamination;
rotating all subsequent soft-magnetic layers with respect to their previous soft magnetic layers so that said single physical interruption in adjacent laminations are rotated with respect to each other in a way such that the single physical interruption of each individual lamination is evenly distributed over a circumference of the set of flat soft-magnetic laminations to create magnetic symmetry in the set of flat soft-magnetic laminations; and
solidifying the resulting set of soft-magnetic layers.
12. The method according to claim 11 , wherein an electrically insulating material is provided inside said at least one physical interruption.
13. A method for constructing a laminated core for a stator or a rotor of a combined radial-axial magnetic bearing, comprising the steps:
providing a set of flat soft-magnetic laminations, wherein each of said flat soft-magnetic laminations comprises a single substantially circular structure having a single physical interruption in the single substantially circular structure;
assembling a first substack by arranging a first plurality of soft-magnetic layers in such a way that said single physical interruption for induced circulating currents is obtained per lamination layer, and in such a way that said single physical interruption in all adjacent lamination layers coincide;
assembling subsequent substacks by arranging subsequent pluralities of soft-magnetic layers in the same way as the first substack with the first plurality of soft-magnetic layers, but in such a way that all subsequent substacks with their pluralities of soft-magnetic layers and said single physical interruption are rotated with respect to their previous substack with a plurality of soft-magnetic layers in a way such that the single physical interruption of each substack is evenly distributed over a circumference of the set of flat soft-magnetic laminations to create magnetic symmetry in the set of flat soft-magnetic laminations; and
solidifying the resulting set of soft-magnetic layers.
14. The method according to claim 13 , including providing an electrically insulating material inside said single physical interruption.