2020.05 / f
15
Electric Power Generation
Installation and maintenance
LSA R/H 49.1
Low Voltage Alternator - 4 pole
4528 en -
4.8 - 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 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 / PMG < 10V
- Check the speed (or LAM set too high)
Voltage between E+ and E-
AREP / PMG > 15V
- Faulty rotating diodes
- Short-circuit in the main field (check the
resistance)
- Faulty exciter armature
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
