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Maintenance
Loading
Overloading
causes
insulation life.
A winding subjected to a 10°C
temperature rise above the maximum limit for its
class may have its insulation life halved.
Under loading a motor is improper as it lowers the
motor power factor and efficiency which results in
higher power cost.
Temperature
Electrical
apparatus
conditions becomes quite warm.
places may feel hot to the touch, the unit may be
within limits.
If checking total temperature by
winding resistance or imbedded detector (RTD), the
total temperature should not exceed the following:
When operating at full load:
Temp. by
All HP
Resistance
1500HP
or less
Over
Temp. by
1500HP
Embedded
-Under
Detector
7000V
Over
1500HP
-Over
7000 V
When operating at 1.15 service factor load:
Temp. by
All HP
Resistance
1500HP
or less
Over
Temp. by
1500HP
Embedded
-Under
Detector
7000V
Over
1500HP
-Over
7000 V
These
temperatures
temperature for each class of insulation and include
a 40°C ambient temperature.
these temperatures will result in reduced insulation
life.
overheating
and
reduces
operating
under
normal
Although some
Class of Insulation System
B
F
120°C
145°C
165°C
(248°F)
(293°F)
(329°F)
130°C
155°C
180°C
(266°F)
(311°F)
(356°F)
125°C
150°C
175°C
(257°F)
(302°F)
(347°F)
120°C
145°C
165°C
(248°F)
(293°F)
(329°F)
Class of Insulation System
B
F
130°C
155°C
175°C
(266°F)
(311°F)
(347°F)
140°C
165°C
190°C
(284°F)
(329°F)
(373°F)
135°C
160°C
185°C
(275°F)
(320°F)
(365°F)
130°C
155°C
175°C
(266°F)
(311°F)
(347°F)
represent
the
maximum
Operation above
Vibration
Most problems can be detected when inspected
visually. Check for;
1. Loose or missing parts, such as fan blades,
nuts, bolts, screws, couplings, etc.
2. Accumulation of dirt on fan or rotor.
3. Associated equipment - Disconnect equipment
to determine where the vibration is being
generated.
4. Foundation construction - Base, grouting and
associated equipment supporting drives must be
in good condition. Vibration can be amplified by
weak construction. Vibration of base just below
motor feet should not exceed 25% of motor
vibration.
5. History - When was vibration first noted? Was
there a change in loading and/or duty of
equipment? Has ambient vibration changed?
H
More important than the actual vibration is the
vibration change over a period of time.
Corrective Maintenance
Two factors that require corrective maintenance are
electrical failure or mechanical failure. The first sign
of
electrical
resistance.
preceded by excessive bearing noise or heat.
Low Insulation Resistance
Factors that usually cause low insulation readings
are:
1. Dirty windings (oil, dust, grease, salt, etc.).
H
2. Excessive moisture.
3. Mechanically damaged insulation.
4. Heat deterioration
Dirty windings can be cleaned and moist windings
dried; however, items 3 and 4 require extensive
repairs by a certified service center.
Flying dirt, dust or other particles.
May cause eye injury.
Wear safety glasses and dust mask when using
compressed air.
- 16 -
failure
is
usually
low
Mechanical
failures
CAUTION
insulation
are
usually
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