13
INSTALLATION AND MAINTENANCE
LSA R 49.1 Air/air heat exchanger
ALTERNATORS - Ex II 3 G
SERVICING - MAINTENANCE
4081 en - 09.2006 / a
LEROY-SOMER
4.4 - Mechanical defects
4.5 - Electrical faults
Fault
Possible causes
Bearing
Excessive overheating of one or both
bearings (temperature > 80°C on the
bearing retainers with or without abnormal
noise)
- End shields incorrectly aligned (flanges not properly fitted).
- If the bearing has turned blue or if the grease has turned black, change the
bearing.
Abnormal
temperature
Excessive overheating of alternator housing
(more than 40 °C above the ambient
temperature)
- Air flow (intake-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
Vibration
Excessive vibration
- Misalignment (coupling)
- Defective mounting or play in coupling
- Rotor balancing fault
Excessive vibration and humming noise
coming from the machine
- Alternator operating in single-phase mode (single-phase load or faulty contactor
or installation fault)
- 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 winding
- 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 diodes
- Armature short-circuit
The alternator builds up but its voltage
disappears when the battery is
removed
- Faulty AVR
- Field windings disconnected
- Main field winding open circuit - check the resistance
Voltage too low
Check the drive speed
Correct speed
Check the AVR connections (AVR may be faulty)
- 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
- 1 faulty diode
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+
and E- on the AVR
Voltage between E+ and E-
AREP < 10V
- Check the speed (or LAM set too high)
Voltage between E+ and E-
AREP > 15V
- Faulty rotating diodes
- Short-circuit in the main field. Check the resistance
- Faulty exciter armature.
(*) Caution :
For single-phase operation, check that the sensing wires coming from the AVR are correctly connected to the operating 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
(**) Caution :
Internal protection may be activated (overload, open circuit, short-circuit)