Specifications

12
LEROY-SOMER
2011.01/ h
Installation and maintenance
LSA 46.2 - 4 POLES
ALTERNATORS
3856 en -
4.4 - Mechanical defects
Fault Action
Bearing
Excessive temperature rise in one or
both bearings (bearing temperature more
than 80 °C) 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)
- Check the end shield alignment (ange not properly tted)
Abnormal
temperature
Excessive temperature rise in the
alternator housing (more than 40° C
above the ambient temperature)
- Air ow (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 (Engine - Alternator)
Excessive vibration and humming noise
coming from the machine
- Phase imbalance
- Stator short-circuit
Abnormal
noise
Alternator damaged by a signicant
impact, followed by humming and
vibration
- System short-circuit
- Mis-paralleling
Possible consequences:
- Broken or damaged coupling
- Broken or bent shaft extension
- Shifting and short-circuit of revolving eld winding
- Fan fractured or coming loose on shaft
- Irreparable damage to rotating diodes, AVR, surge suppressor
4.5 - Electrical faults
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 open circuit (check winding)
- Revolving eld coil 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
- Revolving eld coil 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 the
AVR stability
potentiometer
If no effect: try normal or fast stability
modes (ST2)
- Check the speed: possibility of cyclic irregularity
- Loose connections
- Faulty AVR
- Speed too low when on load (or AVR 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- (DC)
SHUNT / AREP / PMG < 10V
- Check the speed (or AVR LAM set too high)
Voltage between E+ and E-
SHUNT / AREP / PMG > 15V
- Faulty rotating diodes
- Short-circuit in the revolving eld coil. Check the resistance.
- Faulty exciter armature. Check the resistance.
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
- Revolving eld coil open circuit or short-circuited
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