Maintenance
Temperature
Electrical apparatus operating under normal conditions becomes quite warm. Although some 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:
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| Class of Insulation System | |||
|
| B | F | H | |
Temp. by | All HP | 120°C | 145°C | 165°C | |
Resistance | (248°F) | (293°F) | (329°F) | ||
| |||||
| 1500HP | 130°C | 155°C | 180°C | |
| or less | (266°F) | (311°F) | (356°F) | |
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| |
Temp. by | Over |
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| |
1500HP | 125°C | 150°C | 175°C | ||
Embedded | (257°F) | (302°F) | (347°F) | ||
Detector | 7000V |
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| |
| Over |
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| |
| 1500HP | 120°C | 145°C | 165°C | |
| (248°F) | (293°F) | (329°F) | ||
| 7000 V |
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| |
When operating at 1.15 service factor load:
|
| Class of Insulation System | |||
|
| B | F | H | |
Temp. by | All HP | 130°C | 155°C | 175°C | |
Resistance | (266°F) | (311°F) | (347°F) | ||
| |||||
| 1500HP | 140°C | 165°C | 190°C | |
| or less | ||||
| (284°F) | (329°F) | (373°F) | ||
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| ||||
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Temp. by | Over |
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| |
1500HP | 135°C | 160°C | 185°C | ||
Embedded | (275°F) | (320°F) | (365°F) | ||
Detector | 7000V |
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| |
| Over |
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| |
| 1500HP | 130°C | 155°C | 175°C | |
| (266°F) | (311°F) | (347°F) | ||
| 7000 V |
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|
| |
These temperatures represent the maximum temperature for each class of insulation and include a 40°C ambient temperature. Operation above these temperatures will result in reduced insulation life.
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?
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 failure is usually low insulation resistance. Mechanical failures are usually 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.).
2.Excessive moisture.
3.Mechanically damaged insulation.
4.Heat deterioration
Dirty winding can be cleaned and moist windings dried; however, items 3 and 4 require extensive repairs by a certified service center.
CAUTION
Flying dirt, dust or other particles.
May cause eye injury.
Wear safety glasses and dust mask when using compressed air.
Cleaning
Clean the outside of the motor regularly. Actual conditions existing around the motor dictate the frequency of cleaning operations. Use the following procedures as they apply.
1.Wipe off dust, dirt, oil, water, etc., from external surfaces of the motor.
2.Remove dirt, dust, or other debris from ventilating air inlets and exhausts. Do not operate motor with air passages blocked or restricted.
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