Page 165 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

MAINTENANCE OF MOTORS

8.20 CHAPTER EIGHT

14. If there are no defects in the core or windings of the stator, perform these tests on the
stator windings and record the results:
● Insulation resistance and polarization index tests
● Terminal-to-terminal resistances (winding resistances)
● DC high-potential test
● Surge (impulse) test

Rotor Work
15. If there is a dust, grease, or oil contamination on the rotor, clean it with low-pressure steam.
16. Inspect the rotor laminations for looseness, cracks, and damage due to rubbing with the
stator and localized overheating.
17. Inspect the rotor shaft fans of the motor for cracks. If there are signs of cracks, perform
dye penetrant and ultraviolet light inspection.
18. Inspect the bars and end rings of the rotor for cracks, looseness, and localized over-
heating. If there are signs of cracks, perform the manual rotation test as well as dye
penetrant and ultraviolet light inspection.
19. Inspect the rotor shaft for cracks.
20. Mount the rotor on a lathe and measure the eccentricity of the shaft. The total indicated
reading should be less than 0.0038 cm (0.0015 in).

Bearings

21. Inspect the bearings for cracks, wear, etc.

Oil and Water Heat Exchangers
If heat exchangers are used, perform the following steps:

22. Perform chemical cleaning of the heat exchanger, using a weak acid solution.
23. Inspect the heat exchanger for erosion and corrosion.
24. Perform a hydrostatic pressure test to confirm the integrity of the heat exchanger. The
pressure of the water during the test should be 1.5 times the design pressure of the heat
exchanger.
25. If there is evidence of corrosion or erosion, perform an eddy current inspection on the
tubes of the heat exchanger. All tubes that experienced a reduction of more than 50 per-
cent in the wall thickness should be plugged. If more than 10 percent of the tubes have
experienced a reduction in wall thickness of more than 50 percent, consideration
should be given to replace the heat exchanger.

Temperature Detectors
26. Perform a visual and a functional check for all resistance temperature detectors (RTDs)
and thermocouples used in the winding or bearings of the motor.

Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com)
Copyright © 2004 The McGraw-Hill Companies. All rights reserved.
Any use is subject to the Terms of Use as given at the website.