Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-01-26
2001-09-18
Mullins, Burton S. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S061000, C310S264000, C310S052000, C310S214000
Reexamination Certificate
active
06291919
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to generators and, more particularly, to a conductive structural interface for an enclosure for a generator rotor.
In a conventional generator having a rotor and a stator, the rotor is provided with field windings that excite the generator while receiving a current from an exciting current source. The stator is provided with armature windings from which electrical power is output. Typical rotor construction requires that a field winding be assembled bar by bar, into radial slots milled into a rotor forging. Containment of the rotor field windings is typically achieved using rotor wedges, rotor teeth and retaining rings.
It is desirable to replace the bar by bar assembly with a solid rotor having parallel slots milled into a rotor forging. With this structure, the containment components could be replaced with a simplified enclosure.
When composite enclosures are loaded with non-uniform centrifugal radial forces, transverse shear is developed, which may introduce significant inter-laminar shear stresses into the composite enclosure. Additionally, the electrical conductivity of composite enclosures is too low to provide adequate electromagnetic shielding for the field winding. It is thus desirable to provide an interface between the enclosure and the field winding that reduces the shear load on the enclosure, provides electromagnetic shielding of the field winding with good electrical contact with the pole, provides a means of discharging ventilation to the air gap, provides axial stiffness to the structure, and enables axial positioning of individual enclosure rings.
BRIEF SUMMARY OF THE INVENTION
In an exemplary embodiment of the invention, an enclosure shield is provided for a rotor enclosure in a generator including a rotor and a stator. The enclosure is formed of a non-metallic tube for containing a magnetic core and corresponding winding assemblies of the rotor. The enclosure shield is formed of an electrically conductive material shaped corresponding to an inside diameter of the rotor enclosure and including ventilation holes. In one arrangement, the enclosure shield is formed of a plurality of pieces. In this context, each of the plurality of pieces includes structure that extends into notches in the magnetic core. Each of the plurality of pieces may be sized to span a pole face of the magnetic core. A minimum thickness of the enclosure shield is preferably greater than an eddy current skin depth.
In another exemplary embodiment of the invention, a rotor in a generator includes a magnetic core having at least two poles, a plurality of winding assemblies, one for each pole, an enclosure formed of a non-metallic tube housing the core and the winding assemblies, and an enclosure shield disposed between the enclosure and the winding assemblies. The enclosure shield is formed of an electrically conductive material and is shaped corresponding to an inside diameter of the enclosure. The enclosure shield includes ventilation holes. Similar to the above-noted exemplary embodiments, the enclosure shield may be formed of a plurality of pieces. In this context, the plurality of pieces adjoin along a quadrature axis and at an axial midpoint of the rotor.
REFERENCES:
patent: 2630463 (1953-03-01), Smith
patent: 2951954 (1960-09-01), Willyoung
patent: 3991333 (1976-11-01), Laskaris
patent: 4139789 (1979-02-01), Hunt
patent: 4146809 (1979-03-01), Reilly
patent: 4930201 (1990-06-01), Brown
patent: 5166569 (1992-11-01), Shervington et al.
patent: 58-46856 (1983-03-01), None
Chari MVK
Ganti Suryaprakash
Kaminski Christopher A.
Srinivas MV
Wang Yu
General Electric Company
Mullins Burton S.
Nixon & Vanderhye P.C.
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