Operation - Siemens sirius System Manual

4.2.3 Operation

Short-circuit protection
Use with external cur-
rent transformers
Environmental conditi-
ons
Auxiliary contact ele-
ments
Coil and auxiliary
switch repetition termi-
nal
SIRIUS System Manual
GWA 4NEB 430 0999-02b
For short-circuit protection of starter combinations consisting of a contactor
and an overload relay, fuses or 3RV13 circuit breakers are required for
starter combinations.
If external current transformers are to be used to operate the 3RB12, the
following things should be taken into consideration. The 3RB12 with the cur-
rent setting range from 1.25 to 6.3 A must be selected.
The secondary current of the 1 A or 5 A current transformer becomes the
primary current of the 3RB12. In the case of 5 A current transformers, the
3RB12 can be set from 1.25 to 5 A (i.e. from 1/4 of to 1 times the trans-
former's rated current). In the case of 1 A current transformers, a signal
> 1.25 A must be generated by looping the line. If the line is looped five
times, a 5 A signal is generated for the 3RB12.
3RU11
The 3RU11 overload relays can be used without restrictions at ambient tem-
peratures of up to 60 °C. This is the result of new bimetals and continuous
temperature compensation (up to 70 °C with derating).
3RB10
A special coating on the PCB and the electronic components ensures reli-
able operation even in corrosive and tropical environmental conditions.
The 3RU11 and 3RB10 overload relays are equipped with a normally closed
contact for switching off the contactor and a normally open contact for the
tripped signal.
The switching contacts have a high switching capacity so that they can
switch contactor coils directly. The overload relays are therefore suitable for
use with a PLC (17 V, 5 mA).
Frame size S00
In the case of direct mounting onto contactors, the auxiliary switch and coil
repeat terminals (A2) are passed through the 3RU1116 and 3RB1016 over-
load relays. This makes wiring much simpler.
Frame sizes S0 - S3
The contactors of these frame sizes are equipped with 4 coil connections. It
is therefore not necessary to pass through the auxiliary switch and coil ter-
minals (A2) of the contactor.
3RU11, 3RB10, and 3RB12 overload relays
4-13