ABB REG316 4 Series Operating Instructions Manual page 242

ABB Switzerland Ltd
E. Setting instructions
Settings:
Magnetic flux
Delay
Over/underfluxing
The overfluxing function is primarily intended to protect the iron
cores of power transformers. Tripping by the function is delayed
to avoid false operation during system transients such as load
shedding.
The magnetic flux is not measured directly. Instead the volt-
age/frequency ratio which is proportional to the flux and easier to
measure is monitored.
Overfluxing can result from either an increase of system voltage
or a reduction of system frequency.
For example, 10 % overfluxing at constant frequency is
equivalent to increasing the value of the U/f ratio to 1.1 U
Typical settings:
V/f-Setting
Delay
MaxMin
3-204
REG 316*4 1MRB520049-Uen / Rev. F
V/f-Setting
Delay
MaxMin
1.1 U /f
N N
5 s
MAX
/f .
N N