Data processing: measuring – calibrating – or testing – Measurement system – Measured signal processing
Reexamination Certificate
2000-01-31
2002-12-24
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Measured signal processing
C702S190000, C702S056000, C702S075000, C702S076000, C073S570000, C073S572000
Reexamination Certificate
active
06499002
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to the testing and evaluation of mechanical systems and, more particularly, to a broadband energy resonance test for noise evaluation of mechanical systems such as generators.
In operation, mechanical systems such as generators produce noise. The “noise signature” of these mechanical systems generally includes components that are attributable to many different aspects of the system operation. In the case of generators, the noise signature may include components that are attributable to, for example, a loose core and keybar rattle.
FIG. 1
shows a cross-section of a simplified conventional dynamoelectric generator
10
shown in U.S. Pat. No. 4,837,471. Generator
10
includes a stator
12
that has a generally annular shape. The outermost portion of generator
10
and stator
12
is the generator frame
13
.
The stator core
14
is built up by stacking a large number of stator lamination sectors
16
together in a sandwich-like relationship. Stator lamination sectors
16
are attached to the stator using keybars. A rotor
20
is rotatably mounted in a cylindrical opening
22
formed along the central axis
24
of stator
12
. That is, rotor
20
is coaxially positioned within stator
12
such that rotor
20
may be freely turned with respect to stator
12
. Rotor
20
and stator
12
include respective windings (not shown). External excitation power is generally supplied to the rotor field windings via slip rings (not shown) coupled to an external power source. Thus, when mechanical energy is applied to rotor
20
to cause rotor
20
to spin on its axis
24
, a moving magnetic field is generated which rotates at the same rate as rotor
20
. This moving magnetic field cuts across the stator windings thus causing an electric current to be generated with the stator field windings.
FIG. 2
discloses a stator
30
which includes a generally annular stator frame
40
, formed by outer wrapper
42
and a plurality of web plates arranged in annular fashion as indicated in the portion of stator
30
shown in perspective. Keybars
50
include opposed ends, one of which is shown as
50
A. A plurality of keybars
50
are situated in respective holes
52
which are machined in the radially inner edge
56
of web plates
44
. Keybars
50
are used to attach lamination sectors
58
to web plates
44
. Each keybar has a cylindrical portion
60
that is situated within holes
52
and a dovetail portion
62
that extends radially inward from cylindrical portion
60
. The dovetail portions
62
of keybars
50
mate with respective dovetail slots
64
in the radially outer curved edge
66
of stator core lamination sectors
58
. The portion of stator
30
shown in
FIGS. 2 and 3
includes one of a plurality of stator slots
70
which contain conventional current carrying conductors
72
. Stator conductors
72
are held in slots
70
by a conventional dovetail retaining bar
74
.
Generators with loose cores emit a single frequency transformer-type humming sound that, when harmonically filled, can be erroneously evaluated as keybar rattle caused by impacting of the dovetail to core iron (punchings). More specifically, keybar rattle is the result of a loose interface between the core iron (punchings) and the sections of the keybar designed to lock the punchings to the bar. Because the noise signature of a mechanical system such as a generator results from different factors, an intelligent and consistent condition-based acquisition and evaluation of noise data is desirable. In particular, it is important to differentiate between noise caused by different factors (e.g., loose core and keybar rattle) and to determine whether the noise data (or particular components thereof such as noise from keybar rattle) is indicative of any condition requiring repair and whether the repair must be done immediately or may be done at some later date.
BRIEF SUMMARY OF THE INVENTION
It is therefore seen to be desirable to accurately determine and evaluate the relative condition of mechanical system designs at different operational conditions.
During operation, mechanical systems emit a signature noise characteristic ranging from single frequency to either a random or harmonically filled spectrum. The method used in a preferred embodiment of the present invention is much like the differentiation (a specific frequency) and the evaluation (harmonic content) of a specific toned musical instrument within a fifty-piece band. The method is based on the theory that the accumulation of harmonic content within a generator noise spectrum creates a consistent signature index number relating to specific mechanical conditions within the generator. The harmonic peak picking and the subtracting of strategically averaged random noise effects create an intelligible representation of specific mechanical system conditions.
In accordance with a preferred embodiment of the present invention, a noise index for a mechanical system is generated by acquiring noise data over a predetermined frequency range. A fundamental harmonic frequency is chosen and this fundamental harmonic frequency is used to mark harmonic and sub-harmonic data bins. The amplitude of the harmonic and sub-harmonic data bins are recorded and a plurality of sub-harmonic bins equally offset from the center of each harmonic frequency are averaged, the average being subtracted from the preceding harmonic level. The results are accumulated as harmonic content levels indicative of a condition of the mechanical system. The results can be used to determine those conditions requiring repair as well as whether the repair must be done immediately or may be done at some later date.
REFERENCES:
patent: 3758758 (1973-09-01), Games et al.
patent: 3842663 (1974-10-01), Harting et al.
patent: 4380172 (1983-04-01), Imam et al.
patent: 4471308 (1984-09-01), Gable et al.
patent: 4837471 (1989-06-01), Kostoss et al.
patent: 4916803 (1990-04-01), Estrada et al.
patent: 4965513 (1990-10-01), Haynes et al.
patent: 5465221 (1995-11-01), Merat et al.
patent: 5523701 (1996-06-01), Smith et al.
patent: 5961464 (1999-10-01), Poland
patent: 6144924 (2000-11-01), Dowling et al.
patent: 6173074 (2001-01-01), Russo
patent: 6239593 (2001-05-01), Burkhardt et al.
patent: 6297742 (2001-10-01), Canada et al.
Finley, William R., Hodowanec, Mark M., Holter, Warren G., An Analytical Approach to Solving Motor Vibration Problems, IEEE Paper No. PCIC-99-XX (no date).*
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 1, ““F” Technology—the First Half-Million Operating Hours”, H.E. Miller.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 2, “GE Heavy-Duty Gas Turbine Performance Characteristics”, F. J. Brooks.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 3, “9EC 50Hz 170-MW Class Gas Turbine”, A. S. Arrao.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 4, “MWS6001FA—An Advanced-Technology 70-MW Class 50/60 Hz Gas Turbine”, Ramachandran et al.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 5, “Turbomachinery Technology Advances at Nuovo Pignone”, Benvenuti et al.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 6, “GE Aeroderivative Gas Turbines—Design and Operating Features”, M.W. Horner.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 7, “Advance Gas Turbine Materials and Coatings”, P.W. Schilke.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 8, “Dry Low NOxCombustion Systems for GE Heavy-Duty Turbines”, L. B. Davis.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 9, “GE Gas Turbine Combustion Flexibility”, M. A. Davi.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 10, “Gas Fuel Clean-Up System Design Considerations for GE Heavy-Duty Gas Turbines”, C. Wilkes.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 11, “Integrated Control Systems for Advanced Combined Cycles”, Chu et al.
“39th GE Turbine State-of-the-Art Technology Seminar”, Tab 12, “Power Systems for the 21st Century “H” Gas Turbine Combined Cycles”, Paul et al.
“39th
General Electric Company
Hoff Marc S.
Nixon & Vanderhye P.C.
West Jeffrey R
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