11
LEROY-SOMER
InstallatIon and maIntenance
LSA 40 - 4 POLES
ALTERNATORS
4455 en - 10.2009 / a
Mechanical defects
4.4 -
Fault
Cause
Bearing
Excessive overheating of one or both
bearings (bearing temperature 80°C above
the ambient temperature) (With or without
abnormal bearing noise)
- If the bearing has turned blue or if the grease has turned black, change the
bearing.
- Bearing not fully locked (abnormal play in the bearing cage)
- End shields incorrectly aligned
Abnormal
temperature
Excessive overheating of alternator frame
(more than 40° C above the ambient
temperature)
- Air flow (inlet-outlet) partially clogged or hot air is being recycled from
the alternator or engine
- Alternator operating at too high a voltage (> 105% of Un on load)
- Alternator overloaded
Vibrations
Too much vibration
- Misalignment (coupling)
- Defective mounting or play in coupling
- Rotor balancing fault (Engine - Alternator)
Excessive vibration and humming noise
coming from the machine
- Phase imbalance
- Stator short-circuit
Abnormal noise Alternator damaged by a significant impact,
followed by humming and vibration
- System short-circuit
- Misparalleling
Possible consequences
- Broken or damaged coupling
- Broken or bent shaft end
- Shifting and short-circuit of main field
- Fan fractured or coming loose on shaft
- Irreparable damage to rotating diodes/AVR
Electrical faults
4.5 -
Fault
Action
Effect
Check/Cause
No voltage at no
load on start-up
Connect a new battery of
4 to 12 volts to terminals
E- and E+, respecting the
polarity, for 2 to 3 seconds
The alternator builds up and its voltage
is still correct when the battery is
removed.
- Lack of residual magnetism
The alternator builds up but its voltage
does not reach the rated value when
the battery is removed.
- Check the connection of the voltage reference to the
aVR
- Faulty diode
- Armature short-circuit
The alternator builds up but its voltage
disappears when the battery is
removed.
- Faulty aVR
- Field windings open circuit (check winding)
- Main field winding open circuit (check the resistance)
Voltage too low Check the drive speed
Correct speed
Check the AVR connections (possible AVR failure)
- Field windings short-circuited
- Rotating diodes burnt out
- Main field winding short-circuited - Check the
resistance
Speed too low
Increase the drive speed
(Do not touch the AVR voltage pot. (P2) before running
at the correct speed.)
Voltage too high Adjust AVR voltage
potentiometer
Adjustment ineffective
Faulty aVR
Voltage
oscillations
Adjust AVR stability
potentiometer
If no effect : try normal / fast recovery
modes (ST2)
- Check the speed : possibility of cyclic irregularity
- Loose connections
- Faulty aVR
- Speed too low when on load (or LAM set too high)
Voltage correct
at no load and
too low when on
load (*)
Run at no load and check
the voltage between E+ et
e- on the aVR
Voltage between E+ and E–
SHUNT < 6V - AREP < 10V
- Check the speed (or LAM set too high)
Voltage between E+ and E–
SHUNT > 10V - AREP > 15V
- Faulty rotating diodes
- Short-circuit in the main field. Check the resistance.
- Faulty exciter armature. Check the resistance.
(*) Warning :
During single-phase operation, check that the sensing wires from the AVR are connected to the correct output terminals.
Voltage
disappears
during operation
Check the AVR, the surge
suppressor, the rotating
diodes, and replace any
defective components
The voltage does not return to the rated
value.
- Exciter winding open circuit
- Faulty exciter armature
- Faulty aVR
- Main field open circuit or short-circuited
(**) Warning :
The AVR internal protection may cut in (overload lost connection, short circuit).
Summary of Contents for LSA 40-4 POLE
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