Device for magnetically suspending a rotor
The device for magnetically suspending a rotor relative to a structure comprises at least one axial active magnetic bearing with a main electromagnet coil disposed in a stator and having load-bearing surfaces placed facing an armature extending essentially perpendicularly to the axis of the rotor. A device for detecting the axial position of the rotor is associated with circuits for servo-controlling the current carried by the main electromagnet coil. A compensation coil is disposed close to the main electromagnet coil, but in a position that is situated away from the load-bearing surfaces of the stator that co-operate with the rotor armature. The compensation coil is connected in series with the main electromagnet coil, but carries current in the opposite direction to that carried by said main electromagnet coil. The device constitutes an axial abutment of optimized capacity without magnetic leakage.
1. A device for magnetically suspending a rotor relative to a structure, the device comprising at least one axial active magnetic bearing with a main electromagnet coil disposed in a first stator secured to the structure and having load-bearing surfaces placed facing a first rotor armature extending substantially perpendicularly to the axis of the rotor and presenting a free peripheral end, a device for detecting the axial position of the rotor, and circuits for servo-controlling the current flowing in the main electromagnet coil, the device further comprising a compensation coil that is disposed close to the main electromagnet coil, but in a position that is situated away from the load-bearing surfaces of the first stator that co-operate with the first rotor armature, the compensation coil being connected in series with the main electromagnet coil and carrying current in a direction opposite to that carried by said main electromagnet coil.
2. A device according to claim 1 , further including at least one radial active magnetic bearing disposed in the vicinity of the axial active magnetic bearing, the radial active magnetic bearing comprising a second stator secured to the structure and provided with electromagnet windings, and a cylindrical second rotor armature of axis coinciding with the axis of the rotor, a device for detecting the radial position of the rotor, and circuits for servo-controlling the current carried by said electromagnet windings of said second stator.
3. A device according to claim 2 , wherein the device for detecting the radial position of the rotor includes at least one sensor interposed between the second stator and the first stator.
4. A device according to claim 3 , wherein the device for detecting the axial position of the rotor is combined with the device for detecting the radial position of the rotor.
5. A device according to claim 1 , wherein the compensation coil is disposed on the peripherally outer wall of the first stator and is situated beyond the free peripheral end of the first rotor armature.
6. A device according to claim 1 , wherein the compensation coil is disposed on the inner peripheral wall of the first stator and is situated facing the base of the first rotor armature that is connected to the rotor.
7. A device according to claim 1 , wherein the compensation coil is disposed on a substantially radial wall of the first stator on its side opposite from the first rotor armature.
8. A device according to claim 5 , wherein an outer protective plate of the compensation coil is fitted on the first stator.
9. A device according to claim 1 , wherein the compensation coil and the main coil of the axial active magnetic bearing are concentric.
10. A device according to claim 1 , further including an electric motor for driving the rotor in the vicinity of the axial active magnetic bearing.