Compact® NSF and NSJ 150 to 600 A Circuit Breakers
Section 4—Trip Units
© 1995–2003 SchneiderElectric All Rights Reserved
12
Electronic Trip
Unit STR23SP and
STR23SP-OSN
(Oversized
Neutral)
Protection Long-time (LT) overload protection, adjustable threshold, based on the actual rms current
Adjustable threshold (1) using six lo base settings (0.5–1) and fine adjustment Ir with eight
settings ranging from (0.8–1)
Non-adjustable tripping time (2)
Short-time (ST) short-circuit protection
Adjustable threshold Im (3)
Fixed time delay (4)
Instantaneous (I) short-circuit protection, fixed threshold (5)
Neutral protection available on standard four-pole circuit breakers; protection level controlled using
three-position switch
4P 3D: no protection
4P 3D + N/2: neutral protection at 0.5 Ir
4P 4D: neutral protection at Ir
Neutral protection for STR23SP-OSN (oversized neutral) available on four-pole circuit breakers
equipped with oversized neutral protection; protection level controlled using three-position switch
I
t
0
1
3
5
Ir Im
2
4
ImIr
STR 23 SP
x Io
-
test
+
90
105%Ir
alarm
x In
713
6
.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
06153065
NSJ250/400N: NSJ400/600N:
4P 3D: no protection 4P 3D: no protection
4P 3D + N/2: neutral protection at 0.8 x Ir 4P 3D + N/2: neutral protection at 0.75 x Ir
4P 4D: neutral protection at 1.6 x Ir 4P 4D: neutral protection at 1.5 x Ir