ABB UNITROL 1020 - Page 176

Chapter 8 - Troubleshooting 
168 3BHS335648 E82 UNITROL 1020 User Manual
Possible causes
Checks, action
Overvoltage during build-up
Check Soft start settings with the oscilloscope
Overvoltage caused by voltage regulator
Field flashing current too high
Machine voltage UM present
Check system data
Check operating mode. For field flashing normally
Auto is used
Check setpoint
Check thresholds of UM Limiter
Check regulator settings
Check design of the field flashing circuit.
Field flashing should deliver 10 to 15% of the no
load excitation current
Machine voltage not stable in no-load operation
Regulator error
Check operating mode. For field flashing Auto is
normally used
Check setpoints
Check parameters of Auto regulator
Setpoint error
Higher, lower inputs unstable
External input setpoint unstable
Control element fault
Check wiring, loose contact UM, Ie
Parallel operation with grid unstable.
Periodic oscillation of reactive and possibly active power
Regulator settings incorrect
Were changes made to the grid configuration?
Additional outputs, loads etc. installed?
Yes: reset regulator
No: check parameters of Auto and PF, Var
regulator