15
INSTALLATION AND MAINTENANCE
LSA 46.2 / 47.1 - 4 POLE
ALTERNATORS
SERVICING - MAINTENANCE
Ref. 2981 GB - 4.33/b - 07.02
LEROY-SOMER
4.3 - Fault detection
If, when commissioned, the alternator does not work
normally, the source of the malfunction must be identified.
To do this, check that :
- the protective devices are fitted correctly
- the connections comply with diagrams in the manuals
supplied with the machine
- the speed of the unit is correct (see section 1.3).
Repeat the operations defined in section 3.
4.4 - Mechanical defects
4.5 - Electrical faults
Fault
Action
Bearing
Excessive overheating of one or both
bearings (bearing temperature 50°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
- Mis-paralleling
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 or AVR.
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)
