Siemens Induction motors/ generators CGII - Manual (Page 16)

- 15 -
Maintenance
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 windings 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 inside and 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. These materials can work
into or be carried into the motor windings and
may cause overheating or insulation breakdown.
2. Remove dirt, dust, or other debris from ventilating
air inlets and exhausts. Do not operate motor
with air passages blocked or restricted.
Rotor Cleaning
Remove rotor. Inspect air vents and remove any
obstructions.
Stator Cleaning
MICLAD™ form wound VPI (vacuum pressure
impregnated) insulated coils may be cleaned with a
quick drying solvent and lint free cloths or steam
cleaned with low-pressure steam, then the entire
stator oven baked at 200°F for 12 hours and then
230°F for 12 hours.
The stator winding insulation resistance should be
measured before and after any cleaning operation.
The windings may be cleaned with a solvent
compatible with the insulation system and oven dried.
Water and detergents with an oven drying cycle may
be used as an alternate on MICLAD™ VPI insulation
systems.
MICLAD™ is a Siemens trademark.
DANGER
Hazardous voltage.
Will cause death, serious injury,
electrocution or property damage.
Disconnect all power before working
on this equipment.
CAUTION
High Voltage.
May damage semi-conductors, small transformers,
voltage regulators, and other devices.
Disconnect from circuit before testing insulation
resistance.