 Previous Page 310.3
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Motor
Disassembly
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 Background The additional damage frequently caused by improper disassembly of a motor adds to the required repair time. Improper disassembly of a motor damages bearings, windings, end bells, and frames. The procedures taught here are intended to protect the equipment, thus shortening repair time. Preparation for disassembly Place the motor to be repaired on a working surface that will be at a comfortable height for the technician. Ensure the motor is in a solid, flat position on the workbench. Inspect the motor. Remove shaft keys and couplings, if necessary. Tag and place any pieces that are removed in a parts pan. Examine the end bells for cracks or other damages that could cause problems. |
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a prick punch to mark the end bells, field frame, and outer bearing caps. Use existing
matchmarks if possible. Examine the end bells to determine the type of bearing housing. End bell removal Never be hasty or careless in disassembling a generator or a motor. Handle the components with care to avoid damaging them, or causing a need for additional adjustment.
If there are bolts through the end bell to the grease retainers, use the correct size wrench to remove these bolts at both ends. Remove end bell bolts. Note any incorrect bolts or missing bolts, lock washers, etc.
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Click on image to
enlarge. Matchmarking |
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 Use a
mallet or wood block and hammer when separating the end bells from the frame. Do NOT use a
chisel.
Remove the end bell. Using the proper tools, loosen the end bell, and slide it over the pipe to clear the motor frame.
Insert a piece of NOMEX paper between the rotor and stator to prevent contact. Remove the jack and pipe. The rotor can be lowered onto the NOMEX paper you installed between the rotor and the stator. Remove, tag, and place the end bell in the parts pan. Use zip close bags for small parts. Remove all bolts from the rear end bell and note any incorrect bolts.
Remove the rear end bell in the same manner as the forward end bell. Tag and place in parts pan.
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Click on image
to enlarge. End Bell Removal
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removal, install the rotor in V-blocks or secure the rotor by other means to keep it from
rolling. Remove the rotor from the motor by carefully sliding it across the previously inserted NOMEX paper. Tag the rotor.
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Click on image to
enlarge. Rotor on V-Blocks |
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| Conduct electrical and mechanical tests. Use a megohm bridge to measure insulation resistance; record the results on the motor data sheet (electrical). Use a low-range bridge to measure phase resistance of windings. Record results on the motor data sheet (electrical). Surge test the winding and record results on the motor data sheet (electrical). Perform a dc high-potential test. If the ground reading is low or the dc high-potential test is unsatisfactory, clean the winding. If the surge test or phase balance test is unsatisfactory, rewind the motor.
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Click on image to
enlarge. Typical Motor Data Sheet Electrical |
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| Conduct
a shaft radial runout test if it has not been
previously done. Record the results on the motor
data sheet (mechanical). Remove bearings from the rotor. Conduct snap gage readings on the shaft bearing journals and bore gage readings on the end bell bearing housings. Record the results. Route the rotor and end bells to the machine shop if repairs are necessary due to results of bearing journal, bearing housing, or shaft radial runout tests. |
Click on image to
enlarge. Shaft Runout Indication
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Never use vise-grips, pipe wrenches, back crescent wrenches, or pliers.
Be extremely careful when inserting
NOMEX paper. Do NOT place your fingers between the rotor and stator.
| Review Questions If you can correctly answer the questions below, you have learned the key points in this lesson. Choose the correct answer for each question, then look at your score below the questions. Review the lesson if you miss any questions. |