MC40-SEF
Doc. N°
MO-0475-ING
Copyright 2012
FW: 1320.38.01.x
Date
06.09.2022
Rev.
1
Pag.
14
of
36
3.4 - IH (3F51) - Third overcurrent protection level
FuncEnab
→
Enable
[Disable / Enable]
Options
→
BI
Disable
[Disable / Enable]
→
2xI
Enable
[Disable / Enable]
→
Trg
Enable
[Disable / Enable]
TripLev
→
IH
5.00
In
(0.50
40.00)
step 0.01
In
Timers
→
tIH
0.05
s
(0.05
60.00)
step
0.01
s
→
t2xI
0.10
s
(0.02
9.99)
step
0.01
s
Description of variables
FuncEnab
: If disable the function is deactivated
BI
: Operation controlled by Blocking Digital Input
2xI
: Automatic threshold doubling on inrush
Trg
: Function operation triggers the oscillographic wave form capture
(see § Oscillographic Recording)
IH
: Trip level (limited to 40 times In)
t2xI
: Trip time delay
tIH
: Trip time delay
Trip when
: The
current trip level is exceeded for time “tIH”.
When the function is tripped
:
Signalization
=
Led “Trip” is illuminated
Last Trip
= Is recorded
Function reset when
: The current drop below 95% IH.
Led reset when
: push-button is pressed
3.4.1
–
Automatic doubling or Overcurrent thresholds on current inrush
For some of the phase Overcurrent functions it is possible to have the set trip level [Is] automatically
doubled when strong inrush current is detected.
If at circuit Breaker switch-on (i.e. when the input current rises from zero to a minimum measurable value)
the current increases from 0 to 1.5 times the rated value [In] in less than 60ms, the set minimum pick-up
level [Is] is dynamically doubled ([Is]
→
[2Is]) and keeps this value until the input current drops below
1.25xIn or the set time [t2xI] has elapsed.
This functionality is very useful to avoid spurious tripping of the instantaneous or short-time delayed
Overcurrent elements that could be experienced at switch-on of reactive loads like Transformer or
Capacitors.
