Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-09-18
2001-10-09
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S254100
Reexamination Certificate
active
06300702
ABSTRACT:
TECHNICAL FIELD
The present invention generally is related to electrical machines, especially motors, and more precisely is directed to the structure of the stator or rotor assembly thereof.
BACKGROUND OF THE INVENTION AND PRIOR ART
Electrical machines have a stationary element and a movable element. The movable element may be a rotating element or a linearly movable element. The interaction between the stationary element and the movable element is based on the interaction of a magnetic field generated by either the stationary element or the movable element and electric currents in a winding on the movable element or the stationary element, respectively. The interaction is such that the direction of the current, the direction of the magnetic field and the direction of the movement are at substantially right angles to each other, e.g. along an x-direction, a y-direction and a z-direction of a right-angled co-ordinate system.
The winding comprises a plurality of coils wound around teeth of a soft magnetic material normally consisting of steel laminations in order to reduce the eddy currents.
Although the winding can be wound on the stationary element or on the movable element, the following description will be limited to the winding being part of a stator assembly.
Conventionally, the stator assembly of an electrical machine has a stator core formed of a stack of steel laminations. As an alternative to the use of steel laminations, the stator core may be formed from iron powder, as exemplified by U.S. Pat. No. 4,947,065 disclosing a stator moulded in one-piece, and by International Patent Application WO95/12912 disclosing a stator comprising a plurality of separate and substantially identical parts.
By its very nature any compacted, non-sintered material will not be fully dense. This means that soft iron powder currently available will have permeabilities that are lower than the permeabilities obtainable with steel laminations. However, magnetic powder composites could offer advantages such as isotropic magnetic behavior, reduction in iron losses at high frequencies, improved thermal characteristics and flexible design and assembly.
SUMMARY
An object of the present invention is to provide an electrical machine element, specifically a stator assembly, which reduces the cost of the machine without loss of performance. An electrical machine element in accordance with the present invention is characterized by the features specified in appended claim
1
. Preferred embodiments of that electrical machine element are defined in the dependent claims.
Thus, the present invention is related to a combination of a core made of a magnetic powder material and having a yoke and a plurality of teeth spaced in a first direction along the yoke and extending therefrom in a second direction. Here, the spaces between the teeth define spaced winding slots. Further, a winding carried by the core has coil turns located around the teeth and in the winding slots.
According to the invention, the combination assembly is characterized in that each tooth and an adjoining part of the yoke have varying dimensions in a direction transverse to the plane defined by said first and second directions in order to adjust the magnetic flux to a desired or optimal flux density in each part of the magnetic flux path in the core.
In a first embodiment, the core and the winding constitute a stator assembly for a rotational electrical machine. Therefore, the core has an annular yoke and a plurality of teeth spaced circumferentially on the annular yoke, and the spaces between the teeth define circumferentially spaced winding slots.
In a preferred embodiment, the teeth extend radially from the yoke, and each tooth and the adjoining part of the yoke have varying axial dimensions.
Alternatively, the teeth may extend axially from the yoke in which case each tooth and the adjoining part of the yoke will have varying radial dimensions.
The teeth of the core may have a rounded profile such that sharp bending of the coil turns is eliminated and the risk of penetration of the insulation at the corners is reduced. This allows thinner insulation to be used resulting in a substantial thermal benefit.
In a preferred embodiment of the above stator assembly, each tooth forms a separate unit or segment with an adjoining part of the yoke.
As a result of the design according to the present invention, the magnetic field from the coil turn parts is actively used. Thereby, stray losses are reduced and a more efficient machine is provided. Also, a better heat transfer is obtained; specifically by means of the axial extensions of the yoke adjoining the coil turn parts outside the winding slots.
In a further embodiment, the core and the winding constitute a stator assembly for a linear electrical machine, the core having a longitudinal yoke and a plurality of teeth spaced along the longitudinal yoke, and the spaces between the teeth defining longitudinally spaced winding slots. This corresponds to the direction of the movement being along an x-direction, the direction of the magnetic field being along a y-direction and the direction of the varying dimensions of each tooth and an adjoining part of the yoke being along a z-direction of a right-angled co-ordinate system. The improved efficiency may be used for increasing the slot area and/or reducing the width of the yoke. This means a possibility of either reducing the dimensions of the electrical machine with maintained performance or improving the performance with maintained dimensions.
REFERENCES:
patent: 4392072 (1983-07-01), Rosenberry
patent: 4698539 (1987-10-01), Workman
patent: 4947065 (1990-08-01), Ward et al.
patent: 5532531 (1996-07-01), Sakamoto
patent: 6034461 (2000-03-01), Sun
patent: 6087755 (2000-07-01), Suzuki et al.
patent: 6104117 (2000-08-01), Nakamura et al.
patent: 0088992 (1983-09-01), None
patent: 60152245 (1985-12-01), None
patent: 8111968 (1996-04-01), None
patent: WO95/12912 (1995-05-01), None
Jack Alan G.
Mecrow Barrie
Burns Doane , Swecker, Mathis LLP
Hoganas AB
Nguyen Tran
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