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Compact® NSF and NSJ 150 to 600 A Circuit Breakers
Section 4—Trip Units
© 1995–2003 Schneider Electric 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
7
1
3
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