Page 155 - Electrical Equipment Handbook _ Troubleshooting and Maintenance

MAINTENANCE OF MOTORS

8.10 CHAPTER EIGHT

PROBLEM C: Motor overheats. Reduce ambient, increase
Yes
C1 Is ambient temperature too high? ventilation or install larger
No motor.
C2 Is motor too small for present operating Yes Install larger motor.
conditions?
No
Yes Reduce starting cycle or
C3 Is motor started too frequently?
use larger motor.
No
C4 Check external frame. Is it covered with dirt Yes Wipe, scrape or vacuum
which acts as insulation and prevents proper accumulated dirt from
cooling? frame.
No
Remove obstructions or dirt
Feel output from air exhaust openings. Is
C5 Yes preventing free circulation
flow light or inconsistent indicating poor
ventilation? of air flow. If needed, clean
No internal air passages.
C6 Check input current while driving load. Is it No
excessive, indicating an overload? Go to Step C11
Yes
Yes Reduce load or install
C7 Is the driven equipment overloaded?
larger motor.
No
C8 Are misalignments, bad bearings or damaged Yes Repair or replace bad
components causing excessive friction in
driven machine or power transmission system? components.
No
Yes Lubricate. Does motor still
C9 Are motor bearings dry?
draw excessive current?
No
Yes
C10 Are damaged end bells, rubbing fan, bent Yes
shaft or rubbing rotor causing excessive Repair or replace motor.
internal friction?
No
Yes Determine cause of bad
C11 Are bad bearings causing excessive friction?
bearings (See Problem D).
No
C12 Check phase voltage. Does it vary between Yes Restore equal voltage on
phases? all phases.
No
C13 Is voltage more than 10% above or 10% Yes Restore proper voltage or
install motor built for the
below nameplate voltage?
voltage.
No
Yes
C14 Check stator. Are any coils grounded or shorted? Repair coils or replace motor.
FIGURE 8.2 (Continued) Troubleshooting ac motors.

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