Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1995-09-13
1998-03-17
LaBalle, Clayton E.
Electrical generator or motor structure
Dynamoelectric
Rotary
310156, 310261, 310268, 310254, H02K 709
Patent
active
057290652
DESCRIPTION:
BRIEF SUMMARY
MAGNETIC BEARING CELL WITH ROTOR AND STATOR
The invention relates to a rotationally symmetrical magnetic bearing cell with a rotor arranged to rotate about the central axis of the cell having a shaft and at least two axially magnetised permanent magnetic rings fitted an axial distance apart on the shaft, as well as a stator having pole components and two annular coils associated with the rotor end faces whereby the rotor and stator components are arranged in such a way with respect to each other that the permanent magnets generate a magnetic flux which surrounds the central axis toroidally embracing the annular coils.
A magnetic bearing cell having these characteristics is known from DE-C 34 09 047. Its rotor has two axially magnetised permanent magnetic rings which generate the magnetic flux toroidally about the central axis embracing the annular coils. The magnetic flux penetrates the permanent magnetic rings of the rotor which are axially arranged behind each other as well as the peripheral pole components so that a high radial rigidity is attained. The bearing is unstable in the axial direction and therefore requires an active control with respect to this direction. For this purpose annular coils are associated with each of the rotor end faces. Each of these annular coils also generates a toroidal magnetic flux which surrounds the central axis and which superimposes itself on the magnetic flux generated by the permanent magnetic rings. The active control is preferably selected in such a manner that the annular coils do not carry a current when the rotor has attained its nominal position. If the rotor deviates from its nominal position in the axial direction, then a current is applied to the annular coils. The magnitude of the current and its direction depend on the magnitude and the direction of the deviation. Depending on the direction of the current, the toroidal magnetic flux generated by the annular coils has the same or the opposite direction with respect to the magnetic flux produced by the permanent magnetic rings.
SUMMARY OF THE INVENTION
In order to improve radial rigidity of a magnetic bearing of the aforementioned kind, it is proposed to increase the number of permanent magnetic rings on the rotor and to provide in addition on the stator at least one additional permanent magnetic ring which is also axially magnetised (refer to DE-A 41 06 063). These measures increase the flux produced by the permanent magnets, i.e. increase the axial forces and thus give rise to the desired increase in radial rigidity. In order to be able to perform their control task, the annular coils must be capable of generating control fluxes which compensate the increased axial forces. The pre-requisite for this is an increased cross section for the annular coils as well as increased complexity regarding current generation and active control for the coils.
It is the task of the present invention to design a magnetic bearing cell of the aforementioned kind in such a way, that in spite of an improvement in radial rigidity by increasing the number of permanent magnetic rings, active control complexity is not increased.
According to the present invention this task is solved by associating pole components of magnetically conductive material with the peripheral regions of the two axially outer permanent magnetic rings to direct the magnetic flux generated by the annular cells into two substantially independent magnetic flux circuits.
The proposed measures favour the formation of control fluxes directly associated with the annular coils. These cause the magnetic fluxes which are generated by the annular coils and which are substantially independent of each other to only penetrate the respective pole components surrounding the annular coils, a part of the permanent magnetic ring in the vicinity as well as the respective axial and peripheral slit between rotor and stator. Greater resistances are thus not present in these magnetic flux circuits. The magnetic fluxes which chiefly contribute to the axial control of the magneti
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patent: 5084644 (1992-01-01), Harris et al.
patent: 5250865 (1993-10-01), Meeks
patent: 5315197 (1994-05-01), Meeks et al.
patent: 5386166 (1995-01-01), Reimer et al.
patent: 5514924 (1996-05-01), McMullen et al.
Fremery Johan K.
Hodapp Josef
Reimer Peter
Schneider Helmut
Enad Elvin G.
LaBalle Clayton E.
Leybold Aktiengesellschaft
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