Nidec LSA 52.3 - Air Gap Check; General Information; Double-Bearing Machine; Bearings

Electric Power Generation
Installation and maintenance
5382 en - 2022.11 / h
LSA 52.3 / LSA 53.2 / LSA 54.2
Industrial Range Alternators
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5.2 AIR GAP CHECK
5.2.1 General information
Measuring air gap is not always possible due to lack of
access. When the air gap can be reached the measure can
be distorted because of paint and resin coating on the
checked surfaces.
Measure the air gap at different points (minimum four
different points spaced by 90°).
Calculate an averaged value (sum of the measures divided
by the number of measurements).
Compare the averaged value to the measured values.
Main field air gap accuracy:
Acceptable offset (mm)
20% off-centring for an air gap
less than 3mm
15% off-centring for an air gap
4 to 12mm
10% off-centring for an air gap
greater than 18mm
Air gap (mm)
E.g.: for a nominal air gap of 3 mm a measured air gap
value of 2.4 mm is acceptable.
E.g.: for a nominal air gap of 10 mm an air gap measured
value of 8.5 mm is acceptable.
Exciter air gap accuracy:
50% of the nominal value (e.g.: for a nominal air gap of
3 mm a reading of 1.5 mm is acceptable).
Permanent Magnet Generator (optional) air gap tolerance:
50% of the nominal value (e.g.: for a nominal air gap of
1 mm a reading of 0.5 mm is acceptable).
5.2.2 Double-bearing machine
It is not necessary to check the air gap. The rotor is
mechanically centred by its construction. Even after
dismantling and reassembling the machine, the rotor will
return to its position without verification of the air gap.
The exciter air gap of generators type A60 and A62 can be
adjusted on site by 2 jacking screws.
5.3 BEARINGS
5.3.1 General information
NOTE:
Some international studies indicate that over 80% of
roller bearings installed worldwide, regardless of the
context, are damaged prematurely due to a lubrication
problem.
To preserve your machine we recommend closely
fulfilling the recommendations of this manual.
They must be lubricated regularly with the same type of
grease as used in the factory. For information concerning
the lubrication quantity and interval, refer to Section 1:
"Characteristics and Performance".
CAUTION:
LUBRICATION MUST BE CARRIED OUT AS PER
SECTION 1 OR AT LEAST EVERY 6 MONTHS
WHICHEVER COME FIRST.
NOTE:
After a relubricating, the bearing temperature may
increase by 10 to 20°C.
This temporary temperature increase may persist for a
few tens of hours.
NOTE:
In case of a "stand by" duty or generator with short
operation cycles, it is recommended to run the
machine for at least 3 hours after each regreasing.
NOTE:
For regreasing period less than 2,000 hours we
recommend installing a continuous lubrication system
to limit the maintenance operator interventions.
This type of system must be deactivated during
machine shut-down.
The grease contained in these systems must not
remain there over a period of more than 1 year.
5.3.2 Cleaning of old bearing grease
This chapter applies in the event of a change in the type of
grease.
Dismantle the machine in order to have access to the
bearing.
Remove the old grease with a palette knife.
Clean the lubricator and the grease removal tube.
For greater cleaning efficiency, use a brush with solvent.