Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1993-01-15
1994-06-07
Stephan, Steven L.
Electrical generator or motor structure
Dynamoelectric
Rotary
310152, H02K 709
Patent
active
053192745
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to magnetic bearings and is in particular concerned with thrust bearings for use in conjunction with rotating shafts.
BACKGROUND PRIOR ART
It is well-known to support a rotatable shaft by means of a magnetic bearing. It is also known to control the axial displacement of such a shaft by means of a magnetic thrust bearing, as opposed to a conventional thrust race. A magnetic thrust bearing comprises a rotor mounted on the rotable shaft whose axial displacement is to be regulated and at least one fixed stator element mounted to associated hardware. The stator element has associated with it the energising windings whereby the position controlling force is generated, and regulated, typically under the control of electronic sensing/positioning circuitry. It is usual to manufacture the rotor component from solid, iron-based alloys and the same material may be used for the stator element or elements. This is acceptable where the thrust load is fairly static and the rate of change of flux is not a significant factor.
However, where there are dynamic load changes accompanied by a high rate of change of flux, solid magnetic components are undesirable because of the eddy currents developed. These result in high power loss and very significant heating of the bearing components. Accordingly, a laminated construction is preferred for such applications, but if such a construction is to be effective, simple radially-directed laminations are unsatisfactory because of the reduction in magnetic surface area in the progressively radially outward direction. It will be noted that a typical lamination thickness is on the order of 0.1 to 0.25 mm. Wedge shape laminations are not a satisfactory solution, because of this fact. One proposed solution is to increase the diameter of the co-operating components, though this does not really address the further problem which arises when the respective rotor and stator laminations do not actually align with one another at their outer periphery. Where there is no alignment, there will be a high reluctance; where there is alignment, there will be a low reluctance. The overall effect is one of rapid changes leading to higher winding losses and to the generation of high frequency transients in the windings.
It is an object of this invention to minimise these problems.
SUMMARY OF THE INVENTION
According to this invention, laminated stator and rotor components for a magnetic thrust bearing each comprise a plurality of generally radially directed laminations whose roots lie along the axis of rotation of a shaft located by the bearing and are characterised by the distal portions of said laminations being progressively twisted relative to said axis such that the width of any lamination in a circumferential direction at any given radial distance from the root corresponds to at least the circumferential separation between adjacent laminations at that distance.
By progressively twisting individual laminations about their point of attachment to a central hub or other support, the effective radial gap between them is minimised, without increasing their thickness. In other words, the effective area of metal as seen in an axial direction is maximised, in contrast to that achieved by radially aligned flat laminations. Preferably the laminations of the stator element are twisted in the opposite sense to those of the rotor, to enhance their mutual alignment in use.
In order that the invention be better understood, an embodiment of it will now be described with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1, 2 and 3 illustrate prior art constructions, and
FIGS. 4 and 4A-4D illustrate the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a solid metal thrust collar 1. In use, it is mounted on a central shaft 2, and disposed between a pair of corresponding shaped stator elements provided with energising windings (not shown or further discussed here). The stator elements would in this case also be
REFERENCES:
patent: 2312101 (1943-02-01), Killam et al.
patent: 2704231 (1955-03-01), Goldsmith
patent: 2725266 (1955-11-01), Mendelsohn
patent: 4180296 (1979-12-01), Habermann
patent: 5204572 (1993-04-01), Ferreira
patent: 5220232 (1993-06-01), Rigney, II et al.
Patent Abstracts of Japan, vol. 7, No. 126 (M-219)(1271), May 31, 1983 & JP, A, 58 042 824, (Daini Seikosha), Mar. 12, 1983.
Haszko D. R.
Stephan Steven L.
The Glacier Metal Company Limited
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