9 – 13
Motor protection function
In the circuit breaker position t
sd
=
0.02 sec., a special protection function for electromotive drives is activated. It prevents the short-time
delayed short-circuit tripping from being activated during the switch-on current peak of electric motors. At the same time, a phase failure
protection is activated
and the time constant for the internally calculated reproduction of the temperature rise and cooling
process is switched over from switchgear protection to motor protection.
Instantaneous short-circuit tripping – I-tripping
If the current setting I
i
is exceeded, the circuit breaker is tripped instantaneously.
Ground-fault tripping – G-tripping
If the trip unit is equipped with a ground-fault protection module, loads can be protected against impermissibly high ground-fault currents.
Trip units ETU745 - 776 can be equipped with it optionally.
Ground-fault protection modules (page 9-45)
The response value I
g
, together with the setting for the delay time t
g
, determines the shutdown of ground-fault currents.
If the zone selective interlocking (ZSI)
is used and the ZSI module is set to "S" or "S+G" the adjusted delay time t
g
is auto-
matically set to 100 ms provided that in the event of ground-fault the circuit breaker does not receive a blocking signal from a downstream
circuit breaker. In this case regardless of the adjusted t
g
value the circuit breaker will trip after 100 ms.
If a blocking signal exists the adjusted delay time t
g
is valid. For safety reasons after 3 s the blocking signal is terminated. Some trip units
can be switched over to an I
2
t-characteristic.
Setting values for I
i
ETU745
OFF: I
i
= I
CW
I
i
= (1.5 / 2.2 / 3 / 4 / 6 / 8 / 10 / 12 × I
n
MAX = 0.8 x I
CW
ETU748
I
i
> I
CW
ETU776
I
i
= 1.5 x I
n
- 0.8 x I
cs
; OFF
:
I
i
= I
CW
Setting values for I
g
Frame size
II
III
A
100 A
400 A
B
300 A
600 A
C
600 A
800 A
D
900 A
1000 A
E
1200 A
1200 A
Setting values for t
g
ETU745 - 748
t
g
= 0.1 / 0.2 / 0.3 / 0.4 / 0.5 sec.
ETU776
t
g
= 0.1 - 0.5 sec.
M
Summary of Contents for UL 1066
Page 56: ...7 5 7 2 Frame size II fused ...
Page 58: ...7 7 ...
Page 63: ...7 12 8 27 210 0 8 27 210 0 8 27 210 0 3 75 95 2 ...
Page 64: ...7 13 ...
Page 65: ...7 14 7 7 Frame size III fuse carriage ...
Page 66: ...7 15 ...
Page 69: ...7 18 7 9 External sensor for neutral conductor WLNCT2 ...
Page 70: ...7 19 WLNCT3 ...
Page 85: ...9 5 I tripping Ground fault tripping ...
Page 231: ...15 12 Pre assembling the locking module Installing 0767 1 2 3 4 6 5 ...
Page 232: ...15 13 1 Socket head cap screw M5 with washer and nut 7 8 Size 4 5 Nm 45 lb in ...
Page 289: ...23 7 23 3 3 Installing arc chutes 1 2 6 5 PH 2 0043 02 3 4 5 6 For frame size III 3 PH 2 ...
Page 298: ...23 16 6 7 8 9 5 2 1 Size 5 mm ...
Page 333: ......