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Dry out procedures
If the insulation resistance readings are below the recommended mini-
mum values specifi ed previously, use one of the dry out procedures
described below. Select the procedure based on the size and location
of the unit, available equipment, and experience of personnel. Before
drying, remove the voltage regulator, and cover all inlet and discharge
openings. Provide an opening at the top of the machine, preferably at the
fan end, for moisture to evaporate.
Drying with external heat: Place heat lamps, space heaters (in addition
to the ones already supplied) or a steam pipe near the windings. Monitor
winding temperatures. Raise winding temperature gradual ly at a rate
of 10-20° F (-12° to -6°
C) per hour up to 200° F (93° C). Measure
insulation resistance at 1-hour intervals. Typically the insulation
resistance will slowly drop while the temperature is coming up, and then
gradual ly increase and level out.
Drying with AC current in the armature: Short circuit the generator
terminals. Provide DC excitation to the brushless exciter fi eld winding.
Insert a current transformer and an ammeter to read full load current.
Run the generator at rated speed. Apply excitation to the exciter fi eld
until rated current is developed. Monitor winding temperatures until they
stabilize. Continue running until insulation resistance values level off.
Monitor winding temperatures. Raise winding temperature gradually at a
rate of 10-20° F (-12° to -6°
C) per hour up to 200° F (93° C). Measure
insulation resistance at 1-hour intervals. Typically, the insulation
resistance will slowly drop while the temperature is coming up and then
gradually increase and level out.
Bearing lubrication
Shielded or sealed ball bearings: Shielded or sealed ball bearings are
factory packed with lubricants and generally can be operated several
years without requiring replenishment or change of the grease. If
repacking the grease is necessary, disassemble the machine, clean the
bearings, and repack the bearings about 1/2 full using a high quality ball
bearing grease, which must be capable of lubricating satisfactorily over a
temperature range of the lowest ambient temperature to 250º F (121
o
C).
Regreaseable ball or roller bearings: In applications where regreaseable
bearings are used, grease fi ll fi ttings and relief valves are incorporated
into the bearing housing. Lubricate the bearings in accordance with the
lubricating instructions attached to the generator.
Sleeve bearings: Lubricate the bearings in accordance with the
lubricating instructions attached to the generator and the bearing
lubrication instructions, which are provided in the manual package as
supplementary material.
NOTICE: Do not apply heat too rapidly. It
could damage the windings.
NOTICE: For specifi c lubrication
instructions, always refer to the bearing
lubrication sheet that came with your manual
or the lube plate on the generator.
