Rockwell Automation 1329R Vertical Mount, In-Line AC Motors - Manual (Page 8)

8 Vertical Solid Shaft Normal Thrust and In-Line AC Motors
Maintenance The fundamental principle of electrical maintenance is to keep the
motor clean and dry. This requires periodic inspection of the motor,
the frequency (depending upon the type of motor) and the service.
Important: In order to retain UL listing, UL listed motors must be
returned to an Allen-Bradley service facility for repairs or
maintenance which requires opening the motor enclosure.
The following items should be checked at regular intervals:
• Windings should be dry and free of dust. Windings may be
cleaned by suction cleaners or by wiping. Nozzles on suction type
cleaners should be non-metallic. Gummy deposits of dirt and
grease may be removed by using mineral spirits. Do not use
gasoline or other inflammable solvents.
• Terminal connections. assembly screws, bolts and nuts should be
tight. They may loosen if motor is not securely mounted and tend
to vibrate.
• Long storage or unusual operating conditions may cause motor
insulation to absorb moisture. Therefore a megger should be used
to check insulation resistance of the motor to ground. Periodic
megger readings should be taken at approximately the same
temperature and humidity conditions to determine possible
deterioration of the insulation. Standards of the IEEE recommend
that the insulation of stator windings of clean dry machines at
room temperature (approximately 25 degrees C or 77 degrees F)
should not be less than:
If the resistance is below this value, follow the corrective
procedure outlined in the Installation section.
• Totally-enclosed, fan-cooled motors require very little attention.
Be sure that the external air chamber of this motor does not
become clogged with foreign material which will restrict the
passage of air.
• Squirrel cage rotors are rugged and in general, give little trouble.
The first symptom of a defective rotor is lack of torque. This may
cause a slowing down in speed accompanied by a growling noise
or perhaps failure to start the load.
This is caused by an open or high resistance joint in the rotor bar
circuit. Such a condition can generally be detected by looking for
evidence of localized heating.
Repairing end rings should be done only by a competent person.
It is recommended that a factory representative be consulted
before attempting to do this work.
Insulation Resistance (meg-ohms) =
Motor Rated Voltage + 1000
1000