Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1993-10-28
1995-01-31
Skudy, R.
Electrical generator or motor structure
Dynamoelectric
Rotary
H02K 709
Patent
active
053861663
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a magnetic bearing cell that is constructed so as to be rotationally symmetrical, this having a rotor that is arranged so as to be rotatable about the central axis of the cell, and incorporating a shaft and two axially magnetized permanent ring magnets that are secured to the shaft so as to be separated axially, as well as a stator that incorporates two annular coils, pole elements, and an annular disk of non-magnetizable material that is highly conductive electrically, said disk extending into the gap between the permanent magnets of the rotor; the components of the rotor and of the stator are so arranged relative to each other that a magnetic flux that surrounds the central axis toroidally is generated.
Magnetic bearing cells of this kind, such as are described in DE-PS 34 09 047, have proved themselves in practice. Because of the fact that the magnetic flux of a single magnetic circuit is used for axial stabilization, for radial centering, and for damping, these magnetic bearing cells have good damping properties as well as relatively good positional characteristics in addition to a simple construction.
Axial and radial stability (rigidity) are important for the positional characteristics of magnetic bearings. Magnetic bearings of the type referred to here are unstable in the axial direction. For this reason, active axial control is necessary. This is effected with the help of ring coils, an axial sensor, and appropriate electronic controllers.
Radial rigidity depends substantially on the strength of the magnetic flux. This is limited because of structural constraints, since the gap between the permanent ring magnets of the rotor, which have to accommodate the ring disk that damps the bearing, is relatively large and thus forms a relatively large magnetic flux resistance. In a magnetic bearing cell of the type discussed herein, an improvement of radial rigidity could be achieved were the magnetic flux generated by the two permanent ring magnets to have a greater effect. However, this would make a substantial enlargement of both the components that generate the magnetic flux and the components that conduct the flux necessary. In the case of rapidly rotating rotors, for which magnetic bearings are particularly well suited, would make additional measures to overcome centrifugal forces necessary. Furthermore, any additional heat that resulted would have to be eliminated.
It is the task of the present invention to bring about a substantial improvement of the radial rigidity of a magnetic bearing cell of the type described in the introduction hereto without the need for any costly measures.
This problem has been solved according to the present invention in that an additional permanent ring magnet is secured to the shaft and arranged between the pole elements of the stator; in that the additional permanent ring magnet forms a gap with the adjacent permanent ring magnet; and that a ring disk that is secured to the stator projects into this gap, this disk carrying, in the vicinity of the rotating permanent ring magnets of the rotor, an axially magnetized stator permanent ring magnet. In a magnetic bearing cell of this type, the additional rotor permanent ring magnet and the additional stator permanent ring magnet are components of the single magnetic circuit that surrounds the axis toroidally, as was previously the case. The gap between the stator permanent ring magnet and the adjacent rotor permanent ring magnets can be kept very small, so that a substantial improvement (by a factor of greater than 4) of the radial rigidity is achieved. In comparison to formerly known magnetic bearing cells, the magnetic bearing cell according to the present invention is somewhat greater only in the axial direction. No additional problems associated with centrifugal force occur.
Additional advantages and details of the present invention are described in greater detail below on the basis of an embodiment that is shown in the drawing appended hereto.
The magnetic bearing cell 1 that is shown in th
REFERENCES:
patent: 2582788 (1952-01-01), Mendeson
patent: 3865442 (1975-02-01), Studer
Fremerey Johan K.
Reimer Peter
Schneider Helmut
Leybold AG
Skudy R.
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