Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-10-28
2001-05-22
Nguyen, Tran (Department: 3746)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S06700R, C310S261100, C277S377000, C277S377000, C277S377000
Reexamination Certificate
active
06236128
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to the power generation industry and, more particularly, to the field of hydrogen-cooled power generators.
BACKGROUND OF THE INVENTION
In the power generation industry, an exciter is often positioned in axial alignment with a generator rotor which, in turn, is positioned in axial alignment with a turbine. The exciter is often a direct current (“DC”) source and provides a current source to the generator rotor
20
through an axial lead (e.g., positive or negative)
22
positioned in an axial rotor bore
24
of the generator rotor body
21
. As shown in prior art
FIG. 1
, an electrical path is provided to and from the axial lead
22
to coils
25
by two or more radial leads
26
which contact the axial lead
22
through radial bores
27
in the body
21
of the generator rotor
20
(see FIG.
1
). The radial leads
26
are attached to the axial lead
22
by threads in the radial bores
27
and corresponding threads on the leads
22
themselves. A threaded spanner nut
30
positioned in a proximal portion of the radial bore
27
conventionally also assists in mounting the radial lead
26
to the axial lead
22
. The radial lead
26
then connects to one of the coils
25
through a strap
29
which is secured to the radial lead
26
by a fastener assembly
28
, and a current path is provided from the axial lead
22
through the radial lead
26
, through the strap
29
, and to the coils
25
. Also, another portion of the coils
25
connects to another radial lead
26
which, in turn, again is connected to the axial lead
22
so that a positive to negative current path is established.
A hydrogen-cooled power generator within such a system often includes a housing which is sealed to prevent leakage of hydrogen gas positioned within the housing. The hydrogen gas is used to cool the generator. The hydrogen gas is conventionally at a much higher pressure within the housing than that of the atmospheric pressure outside the housing. If the hydrogen gas leaks from the housing, for example, the gas is potentially explosive and can cause various ventilation and environmental problems. The generator rotor is also positioned within the housing.
In addition to leakage from suspected locations or openings to and from the housing, other areas of the generator rotor are also susceptible to leakage such as through the axial lead, e.g., due to the pressure differential within and outside the housing. Access to the axial lead, for example, can be achieved by gas passing along outer peripheries of the radial bores. As shown in
FIG. 1
, to prevent such a leakage a complex sealing assembly
40
is conventionally used, including numerous sealing members, e.g., Chevron seals
42
, and sealing hardware, e.g., washers
43
, a spring
44
, spacers
45
. This complex assembly
40
is separate from the radial lead spanner nut
30
, and can take extensive time and be costly to manufacture, can be complex to assemble and install, can be difficult to remove, and can be difficult to handle. For example, if portions of the sealing assembly
40
are not placed into position correctly the first time, then jamming within the radial lead bore
27
can occur. Also, the conventional sealing assembly
40
, for example, requires an axial load applied by the spring
44
in order to activate the seals.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention advantageously provides a radial lead spanner nut assembly and method of sealing a radial lead bore for preventing leakage of hydrogen gas in a hydrogen-cooled power generator which eliminates the need for a separate seal assembly for sealing a radial lead bore within the body of a generator rotor. The present invention also advantageously provides a radial lead spanner nut assembly and associated methods which makes installation, handling, and removal of a seal for a radial lead bore much easier. The present invention additionally advantageously provides an apparatus for preventing leakage of hydrogen gas in a hydrogen-cooled power generator having a radial lead spanner nut assembly which costs substantially less to manufacture without sacrificing reliability. The present invention further advantageously provides a radial lead spanner nut having integrated seals which functions as a self-contained seal cartridge to prevent gas leaks around the radial lead through the radial lead bore and which can easily accommodate various types of power generators.
More particularly, an apparatus is provided for preventing leakage of hydrogen gas in a hydrogen-cooled power generator. The apparatus preferably includes a power generator having a rotor body including a rotor bore and an axial lead positioned within the rotor bore for providing a current path through the rotor and a radial bore formed in the rotor body and extending from an outer surface of the rotor body to the axial lead. The radial bore preferably has a first predetermined diameter and a second predetermined diameter greater than the first predetermined diameter so that a transition region from the first predetermined diameter to the second predetermined diameter defines a bore shoulder. The radial bore also preferably includes bore threads positioned along proximal end portions of the radial bore. A radial lead is positioned in the radial bore and has distal end portions connected to the axial lead of the rotor body. A radial lead spanner nut assembly is preferably mounted to the radial lead and has portions thereof abuttingly contacting the outer peripheries of the radial bore and the radial lead. The radial lead spanner nut assembly preferably includes a radial lead spanner nut body, nut threads positioned on the outer peripheries of the nut body and abuttingly contacting the radial bore along the bore threads thereof, and a plurality of spaced-apart seal channels formed in peripheries of non-threaded portions of the nut body. The plurality of spaced-apart seal channels includes at least a first seal channel formed in outer peripheries of the nut body adjacent non-threaded portions of the radial bore and at least a second seal channel formed in inner peripheries of the nut body adjacent the radial lead. The radial lead spanner nut assembly further includes first and second seal members respectively positioned in the first and second seal channels. The first seal member is positioned to abuttingly contact non-threaded portions of the radial bore, and the second seal member is positioned to abuttingly contact the radial lead.
The present invention also provides a radial lead spanner nut assembly for preventing leakage of hydrogen gas in hydrogen-cooled power generators. The spanner nut assembly is preferably mounted to a radial lead positioned in a radial bore of a generator rotor of a power generator. The radial lead spanner nut assembly preferably has a radial lead spanner nut body, nut threads positioned on the outer peripheries of the nut body for abuttingly contacting a radial bore along the bore threads thereof, and a plurality of spaced-apart seal channels formed in peripheries of non-threaded portions of the nut body. The plurality of spaced-apart seal channels include at least a first seal channel formed in outer peripheries of the nut body adjacent non-threaded portions of the radial bore and at least a second seal channel formed in inner peripheries of the nut body adjacent the radial lead. The radial lead spanner nut assembly also preferably includes first and second seal members respectively positioned in the first and second seal channels. The first seal member preferably abuttingly contacts non-threaded portions of the radial bore, and the second seal member preferably abuttingly contacts the radial lead.
The present invention further provides a method for preventing leakage of hydrogen gas from a hydrogen-cooled power generator. The method preferably includes the steps of mounting a radial lead spanner nut assembly to a radial lead positioned in a radial bore of a generator rotor body of a power generator. The radial lead spanner nut
Nguyen Tran
Siemens Westinghouse Power Corporation
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