Siemens SIRIUS 3RH Series, System Manual

Page: 392 / 786

SIRIUS 3RV2 motor starter protectors
4.5 Configuration
SIRIUS Innovations
392
System Manual, 01/2011, A8E56203870002-03
4.5.4 Motor protection with overload relay function
3RV21 motor starter protectors with overload relay function have the same overload and
short-circuit release characteristic as 3RV20 motor starter protectors. However, the overload
releases have no effect on the motor starter protectors' breaker latching mechanism. In the
event of an overload, the motor starter protector remains on.
The overload release is linked to two auxiliary contacts (1 NO c 1 NC contact)
mounted on the side; these are switched in the event of an overload. The auxiliary contacts
can be evaluated or can be used to disconnect a downstream contactor. The auxiliary
contacts are reset automatically once the motor starter protector has cooled down.
CAUTION
In the overload range the motor starter protector with overload relay function does not
protect itself. Provision has to be made, therefore, to ensure that the current is safely
disconnected by a downstream switching device such as a contactor.
Note
Fixed connection: Auxiliary contacts with motor starter protector
The auxiliary contacts are connected to the right-hand side of the motor starter protector.
The connection is fixed and cannot be removed.
This means that auxiliary releases cannot be mounted on the right-hand side of 3RV21
motor starter protectors with overload relay function.
Reference
More information ... Can be found in the chapter titled ...
About motor starter protector operation Operation (Page 404)
4.5.5 Short-circuit protection for starter combinations
3RV23 MSP for starter combinations
3RV23 MSPs for starter combinations are motor starter protectors without overload releases.
They are always used in conjunction with a contactor and overload relay, as the motor
starter protector alone is not able to protect the motor and itself against overloads.
Function
In the event of an overload, the overload relay trips the contactor. The motor starter protector
remains on. The motor starter protector will only trip as well in the event of a short circuit in
the feeder.
Like the motor starter protectors for motor protection, the short-circuit releases are set to a
fixed value of 13 times the rated current of the device.
Advantage
In the event of tripping due to overload, an automatic or manual reset can be performed
without having to open the control cabinet.