Apparatus and method for inpact testing for electric generator stator wedge tightness

• US 5,295,388 A
• Filed: 01/30/1992
• Issued: 03/22/1994
• Est. Priority Date: 01/30/1992
• Status: Expired due to Term

• Current Assignee: Siemens Energy Incorporated (Siemens AG)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Alford, James W., Noll, John E. Jr., Dailey, George F., Fischer, Mark W.
• Primary Examiner(s): Chilcot, Jr., Richard E.
• Assistant Examiner(s): Dougherty, Elizabeth L.
• Application Number:
  US07/828,099
• Time in Patent Office: 782 Days
• Field of Search: 73/12, 73/865.8, 73/572, 73/582, 73/574, 73/662, 73/12.04, 73/12.06, 73/12.12, 73/12.09, 33/656, 324/207.18
• US Class Current: 73/12.09
• CPC Class Codes: G01M 7/08 Shock-testing

Abstract

Method and apparatus for performing remote impact testing for generator stator wedges and ripple springs. An improved low profile carriage is utilized for correlating wedge displacement data with the force required to displace the wedge. A calibrated test stand, in which exemplary wedges are placed under a known loading via a hydraulic load cell, provides means for generating calibration curve sets. From the graphed forcedisplacement curves generated from wedges placed under a known loading, force and displacement data generated during actual stator testing can be analyzed to measure the tightness or looseness of stator wedges, coils and ripple springs. In the preferred embodiment of the low profile carriage of the present invention, a capacitive sensor is used to directly measure the displacement or vibration of stator wedges as a result of being struck by an impact hammer with a known force.

Claims

1. A method of measuring the tightness of stator wedges in the stator of an electric generator without removing the rotor, the method comprising the steps of:

i. providing a calibration test stand comprising a section of coils and wedges similar to that of the electric generator to be measured;

ii. preloading said section of coils and wedges of the calibration test stand with a first predetermined force and generating a plurality of force-displacement curves obtained by impacting said wedges of the calibration test stand with a second predetermined force and measuring the displacement caused thereby;

iii. calculating a plurality of curve equations from said plurality of force-displacement curves;

iv. striking one of said stator wedges to cause a displacement thereof;

v. measuring the force used to strike the one stator wedge to generate force data;

vi. measuring displacement of the one stator wedge in response to being struck to generate displacement data;

vii. comparing said generated force and displacement data with said plurality of forcedisplacement curves to determine the tightness of the one wedge in said stator.

2. A method of measuring the tightness of stator wedges in the stator of an electric generator without removing the rotor, the method comprising the steps of:

i. providing a calibration test stand comprising a section of coils, filler material, and wedges substantially similar to that of the electric generator to be measured;

ii. preloading said section of coils, filler material, and wedges of the calibration test stand with a first range of predetermined forces measured at the load source and generating a plurality of force-displacement curves obtained by impacting said wedges of the calibration test stand with a second range of forces measured at an impact point and measuring the wedge displacement caused thereby;

iii. calculating a plurality of curve equations from said plurality of force-displacement curves;

iv. striking one of said stator wedges to cause a displacement thereof;

v. measuring the force used to strike the one stator wedge to generate force data;

vi. measuring displacement of the one stator wedge in response to being struck to generate displacement data;

vii. comparing said generated force and displacement data with said plurality of forcedisplacement curves to determine the tightness of the one wedge in said stator.

3. Apparatus for measuring the tightness of stator wedges in the stator of an electric generator without removing the rotor, said apparatus comprising:

a low profile carriage insertable in a narrow gap between the rotor and stator and successively positionable adjacent selected stator wedges;

an impactor carried by said low profile carriage, said impactor striking the selected stator wedge to cause a displacement thereof; and

sensor means mounted on said low profile carriage for directly measuring the peak-to-peak amplitude displacement of the selected stator wedge in response to being struck by said impactor.

4. Apparatus as recited in claim 3, wherein said sensor means comprises a capacitive sensor mounted on said low profile carriage for measuring the maximum displacement of the stator wedge.

5. Apparatus as recited in claim 3, wherein said sensor means comprises a fiber optic sensor mounted on said low profile carriage for detecting light reflected from the selected stator wedge as said wedge is displaced in response to being struck by said impactor.