Siemens UL 489 Operating Instructions Manual page 114

Motor protection function
When the short-time delay is set to 20ms (t
tripping during the turn-on inrush for motors. At the same time, a phase loss sensing function is enabled
constant used for long-time protection is changed from one suitable for bus protection to one suitable for motor protection.
Instantaneous short-circuit tripping – I-tripping
If the current setting I is exceeded, the circuit breaker is tripped instantaneously.
i
Setting values for I
i
ETU745 OFF: I
I
MAX = 0.8 x I
ETU776 I
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.
The response value I , together with the setting for the delay time t
g
Setting values for I
g
I & II
A 100 A
B 300 A
C 600 A
D 900 A
E 1200 A
Setting values for t
g
ETU745
ETU776
If the zone selective interlocking (ZSI)
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
If a blocking signal exists the adjusted delay time t
2
can be switched over to an I
9 – 12
0.02 sec.), a special motor protective function is enabled which prevents short-time 
M
=
sd
= I
i CW
= (1.5 / 2.2 / 3 / 4 / 6 / 8 / 10 / 12 × I
i
CW
= 1.5 x I - 0.8 x I ; OFF : I = I
i n cs i
Frame size
III
400 A
600 A
800 A
1000 A
1200 A
t = 0.1 / 0.2 / 0.3 / 0.4 / 0.5 sec.
g
t = 0.1 - 2.0 sec.
g
 (page 9-14)
is used and the ZSI module is set to "S" or "S+G" the adjusted delay time t
value the circuit breaker will trip after 100 ms.
g
is valid. For safety reasons after 3 s the blocking signal is terminated. Some trip units
g
t-characteristic.
n
CW
 Ground-fault protection modules (page 9-44)
, determines the shutdown of ground-fault currents.
g
 (page 9-13)
and the thermal time
is auto-
g