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3VT3 Molded Case Circuit Breakers up to 630 A
Overcurrent releases
4/19
Siemens LV 36 · 2008
4
Overcurrent releases ETU DP-Distribution
Protecting lines and transformers
The 3VT9 3..-6AC00 release is intended for 3VT3763-.AA36-
0AA0 and 3VT3763-.AA46-0AA0 switching units. Operation of
the release is controlled by a microprocessor. The release is
equipped with a thermal memory that can be disabled by turn-
ing a switch on the front panel from position T
(t)
to position T
(0)
.
After disabling the thermal memory, the thermal release remains
active. The operational state 70% of
I
r
is signalled by an LED in-
dicator that flashes green in a 1.5 s interval. As the load grows,
the blinking frequency of the diode increases. In case of a load
larger than 110% of
I
r
, this LED will turn red and just before trip-
ping will begin to blink red.
On the lower part of the release cover are two photocells for
communicating with the prospective signalling unit.
The releases have tripping characteristics especially designed
for practical purposes that provide for optimal exploitation of
transformers up to 1.5
I
r
.
The releases have simple adjustment of the tripping character-
istic. Set-up includes only the rated current and the short-circuit
tripping level at 4
I
r
or 8
I
r
.
Tripping characteristics
NSO0_00357
x
I
n
1 2
5
20
50
10
0.1 0.2 0.5
I
r = 575 A.630 A ~
I
i = 7 kA
4x
12.5x
4x
12.5x
4x
12.5x
4x
12.5x
4x
12.5x
4x
12.5x
I
I
n
= 250 A
I
n
= 400 A
I
n
= 630 A
I
i
I
i
I
i
I
n
= 250 A
I
n
= 400 A
I
n
= 630 A
L
I
r
I
i
0.02
0.02
0.05
0.05
0.01
0.01
20
200
2000
50
500
5000
10
100
1000
10000
t
[s]
0.01
0.02
0.05
0.1
0.1
0.1
0.2
0.5
1
2
5
I
r
min.
max.
3
3