Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1994-09-26
1997-04-01
LaBalle, Clayton E.
Electrical generator or motor structure
Dynamoelectric
Rotary
384624, H02K 709, F16C 4100, F16C 3204
Patent
active
056169760
DESCRIPTION:
BRIEF SUMMARY
The invention concerns an auxiliary bearing system for a rotor, which is supported without contact in floating manner, particularly by generation of a magnetic field between stator and rotor. The auxiliary bearing system consists of mechanical auxiliary bearing elements, which are attached to the stator at a small distance from the rotor and operate when the rotor jumps radially out of position.
Auxiliary bearing systems for contactless mounted rotors are necessary in order to intercept error functions, particularly in the case of overly high radial force stress of the rotor. The auxiliary mounting, which has roller and/or glide bearing elements, is arranged on the stator such that the rotor maintains its contactless position in normal operation and is only supported by the auxiliary bearing system in the case of an impermissible radial deflection.
The design of the auxiliary bearing system has considerable importance due to the loading of the auxiliary bearing elements in the case of engagement; see, e.g., the journal "Magnetic Bearing Insights`, Vol. 1, No. 4, November 1991, pages 8-10. The load of the auxiliary bearing elements is formed by the precession counter-rotational motion, which is caused by the friction between the rotor and the auxiliary bearing elements and increases progressively with radial bearing forces, and this can lead to disruption of the rotor and, in unfavorable cases also to the disruption of the rotor environment due to the overly high bending of the rotor.
Knowing this state of affairs, auxiliary bearing constructions are proposed which counteract the stimulation of precession motion. It is known from DE OS [unexamined] 2,741,062 to support the rotor shaft not as usual with an auxiliary bearing element surrounding the rotor shaft (outer support), but rather to intercept the rotor during an undesired radial deflection by means of an auxiliary bearing element introduced into an axial borehole in the rotor shaft (inner support). In both cases, upon contact with an auxiliary bearing element, a tangential frictional force arises in the auxiliary bearing, which drives the rotor radially outward due to the gyroscopic principle (gyroscope forces). As a consequence of these forces, the rotor is progressively tightened in the auxiliary bearing in the case of the outer support, since the gyroscope forces increase with increasing bearing force. In the case of an inner support, on the other hand, an unloading of the auxiliary bearing system occurs, however, due to the rotor pressing outwardly, and the rotor has the tendency to lift off from the contact surface in the auxiliary bearing element. This is, in principle, the advantage of an inner support,
Of course, contrasted with this advantage of the inner support, there is the disadvantage that a torsional moment is transferred onto the rotor by the contact friction in the auxiliary bearing element in such a way that the rotor can be flung around the supporting auxiliary bearing element and is no longer free of a "synchronous movement" caused thereby. This is particularly the case if the rotor frequency passes through a synchronous resonance of the auxiliary bearing system.
Thus while the outer support acts by stimulating counter-rotation and thus synchronous damping, the inner support has the opposite effect. Both types of support lead to undesired kinetic states of the rotor.
An object of the invention is to combine the advantages of the inner support with those of the outer support in an effective manner.
This and other objects are attained in accordance with one aspect of the invention directed to an auxiliary bearing system, comprising a stator and a rotor which is mounted to the stator to float without contact by generation of a magnetic field between the stator and the rotor. A first auxiliary bearing element is attached to the stator and it has a contact surface, spaced at a first distance from an outer surface of the rotor, with which the outer surface of the rotor is engageable when the rotor radially jumps out of position. A second
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Auxiliary Bearing Design, Insights, vol. 1, No. 4, Nov. 1991 pp. 8-10.
Fremerey Johan K.
Rabiger Jurgen
Forschungszentrum Julich GmbH
LaBalle Clayton E.
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