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 ELECTRICAL
Motors and Generators-Continued
end play
overheating
looseness of windings
charred wedges
broken
cracked
loosely welded or soldered rotor bars or joints
cracked end rings in squirrel cage motors
loose field spools and deteriorated leads and connections in
synchronous motors
deteriorated insulation in wound rotors
n Roto-Stator Gaps:
Check gaps on 5 hp or larger induction motors, particularly of the
sleeve bearing type
Where practicable, measure and record gaps on the load, pulley or
gear end of the motor
Measure at 2 rotor positions, 180 apart, 4 points for each rotor
position. If there is more than 10% variation in gaps, arrange for
realignment
n Mechanical Parts:
corrosion
improper lubrication
misalignment
end play
inadequate chain or belt tension
n Insulation Resistance:
Test insulation resistance of motor and generator windings.
Compare results with table below
Insulation resistance values are arbitrary and should be correlated
with operating conditions, exposure to moisture, metallic dust, age,
length of time in service, severity of service, and maintenance levels
7-35
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