Specifications

10
COMPACT
®
NS circuit breaker
I
t
0
1
3
5
Ir Im
2
4
COMPACT
®
NS circuit breaker: functions and characteristics
Trip units
Trip units for COMPACT
®
NSJ400 and NSJ600 circuit breakers
Electronic trip unit STR23SP
E28021
E21003
Other functions
Indications
Load indication (LED) in front (6):
■ Goes on at: 90% of Ir threshold;
■ Flashes at: >105% or more of Ir threshold.
Test
■ Test connector in front (7) for connection to a mini test kit or calibration test kit
(see page 13) to check circuit breaker operation after fitting the trip unit or other
accessories;
Protection
■ LT (long-time) overload protection, adjustable threshold, based on the actual rms
current:
❑ Adjustable threshold (1) using six lo base settings (0.5 to 1) and fine adjustment Ir
with eight settings ranging from (0.8 to 1);
❑ Non-adjustable tripping time (2);
■ ST (short-time) short-circuit protection:
❑ Adjustable threshold Im (3);
❑ Fixed time delay (4), with or without constant I
2
t function;
■ I (instantaneous) short-circuit protection, fixed threshold (5).
Setting example
400 x 0.5 x 0.8 = 160 A
What is the overload protection
threshold of a COMPACT
®
NSJ400
circuit breaker equipped with trip unit
STR23SP where Io = 0.5 and
Ir = 0.8 ?
Answer:
In x Io x Ir = 400 x 0.5 x 0.8 = 160 A
The same trip unit with the same
settings, mounted on an NSJ600
circuit breaker will have the following
tripping threshold:
In x Io x Ir = 600 x 0.5 x 0.8 = 240 A
E25979
x In
Ir
x Io
.8
.85
.9
.95
1
.88
.93
.98
Io
.5
.63
.7
.9
1
.8
ImIr
STR 23 SP
x Io
-
test
+
90
105
%Ir
alarm
x In
1
2
4
3
.5
.63
.7
.9
1
.8
.85
.9
.95
1
.88
.93
.98
.8
2
3
4
56
7
9
x Ir
Io = sensor
Ir
long time
Im
short time