2018.01 / a
8
Electric Power Generation
Installation and maintenance
R121
AVRs
5657 en -
7 - TROUBLESHOOTING CHART
Symptom
Cause
Action
No voltage
build-up
Fuse blown
Check and replace
Low residual voltage across U
and N terminals
If the generator’s residual voltage at rated speed
is less than 2.5 VAC (L-N), disconnect the AVR
and connect a 24 VDC battery, keeping F1 as
positive and F2 as negative.
Connecting a freewheel diode (BY 127 or
equivalent) across the field with the diode cathode
to F1 and the anode to F2 during field flashing will
help restore the residual voltage.
WARNING:
Remove the diode (BY-127) after field flashing.
The 24 V battery positive terminal must only be
connected to F1 and the negative to F2.
Swapping the connection will cause diode BY127
to explode instantly.
Incorrect wiring
Check wiring
Rotating diodes and/or fuse
failed
Check and replace
Voltmeter on the front
defective
Check and correct
AVR defective
(repeated fuse blowing)
Replace after performing a static test
Earthed exciter field
Check and correct
High voltage
build-up
Incorrect setting
Check and correct
AVR defective
Perform a static test and replace if necessary
Low voltage
build-up
Low prime mover speed
Check and correct
Incorrect setting
Check and correct
AVR defective
Replace the AVR
Voltage oscillation
Incorrect stability
potentiometer sealing
Turn clockwise until hunting stops
Prime mover speed hunting
Check and adjust the controller
Load hunting, fluctuates
rapidly
Check and correct
High percentage of non-linear
loads
Check and reduce the non-linear load
High reactance in generator
(during non-linear loading)
Consult the generator manufacturer
Incorrect
regulation
The exciter field’s requirement
is too high
Wrong selection or very low P.F. load.
Check and correct.
Prime mover speed drops too
much when on load (kW load)
Adjust the controller and reduce the active load
