50 Hz: G625 - G690 - G750XW/XF
OPERATION & MAINTENANCE MANUAL
75
60 Hz: G655 - G750 - G800 - G850XW/XF
Voltage too
high.
Adjust AVR voltage
potentiometer.
Adjustment ineffective.
- Faulty AVR.
- 1 faulty diode
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 EAREP
/ PMG < 10V
- Check the speed (or LAM set too high)
Voltage between E+ and EAREP
/ PMG > 15V
- Faulty rotating diodes.
- Short-circuit in the revolving field coil.
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