Application of Fiber Optic Sensors for Stator End Winding Vibration Monitoring. M. Sasic, R. Sadanandan, G. Stone Iris Power Qualitrol

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1 Application of Fiber Optic Sensors for Stator End Winding Vibration Monitoring M. Sasic, R. Sadanandan, G. Stone Iris Power Qualitrol

2 What is endwinding? Endwinding Slot

3 Objectives of the Support System Keep stator coils in stator slots Keep together stator coils outside slots Provide support against steady and sudden forces Provide flexibility for thermal expansion

4 Challenge is to design a stator end-winding support structure and produce a structure that is tough enough to withstand the millions of daily cycles of electromagnetic forces, strong enough to survive system events without undue damage, and yet flexible enough to allow thermal expansion to occur safely

5 Problem is How to find out are design and manufacturing appropriate for forces that will be present in operation of rotating machine Off-line testing-bump test On-line monitoring

6 Forces can be:

7 Bump Test A bump test is a type of vibration test The machine is instrumented with one or more vibration transducers, and it is then impacted with a hammer The resulting spectrum will contain peaks that correspond to the natural frequencies of the machine

8 Bump Test

9 What is Modal Analysis? Modal analysis is the term used to describe the modeling of patterns of vibration, or mode shapes for a given structure. In order to reduce the effects of vibration, structural analysis of equipment can be used to predict the mode shapes and make structural modifications as required.

10 From 0 to 4 nodal lines

11 Why is this important? The design of the stator windings should be such that the critical oval (2-pole) and square (4-pole) resonant frequencies are away from the operating frequencies of the machine (50Hz/100Hz or 60Hz/120Hz. If the frequencies are too close to operating frequency, or if they shift close to operating frequency at the operating temperatures, the structure would become resonant and the vibration will increase under the driving forces generated by the rotating magnetic fields.

12 Reasons for EWV monitoring Various motivations may determine how many sensors and where will be installed: A: Typical, preventive installation B: Installation on machine with known design issues or after visual inspection findings

13 On-line EWV Sensors Single, dual or triaxial Mechanical not acceptable Optical Different methods used in design of optical sensors, resulting in different properties, like bandwidth and resolution

14 EWV Sensor Requirements It must be able to operate in a temperature range of stator winding It must not contain conductive components in order to avoid interference with high voltage in end-winding It must have a bandwidth from Hz and resonance frequency above 2.5 khz in order to eliminate any possible interference within the measuring range

15 Endwinding Vibration Accelerometer

16 Sensor Locations Typical installation usually consists of 6 sensors on each endwinding Locations should be determined by bump test/modal analysis Without the test, sensors are usually symmetrically placed around the winding

17 Validity of Bump Testing Off-Line vs. On-Line methods Effect of temperature increase on stiffness

18 Case Study The experimental results were done with the help of Motion Electric in Mississauga, Canada

19 Case Study Both endwindings were tested at three temperatures: 22, 60 and C

20 Case Study 24 test points were selected at each end Three axes were defined as X-radial, Y- tangential and Z-axial

21 Case Study-Point 1 at 22 C

22 Case Study-Point 1 at 58 C

23 Case Study-Point 1 at 90 C

24 Modal Analysis

25 NCE End Position 2 Cold and Hot

26 NCE End Position 2 Cold and Hot

27 Two ends, three temperatures

28 Frequency vs. Temperature

29 Conclusions The natural frequencies of the endwinding mode shapes decreased by 9-12 Hz as temperature increased from 22 C to C. The characteristics of the mode shapes including anti-node locations remain stable across the range of temperatures. This information is important to establish proper location for installation of endwinding vibration sensors.