Siemens SIRIUS 3RH Series, System Manual

Page: 172 / 786

SIRIUS 3RT2 contactors/contactor assemblies
2.7 Accessories
SIRIUS Innovations
172
System Manual, 01/2011, A8E56203870002-03
Surge suppressor Suitable for
Control
voltage
Overvoltage
is limited ... Effect Advantages/disadvantages Preferred
application
Advantag
es

Energy absorption

Non-critical
dimensioning

Simple
implementation
Varistor AC/DC To varistor
voltage
 OFF-delay
becomes only
slightly longer
(2 to 5 ms)
Disadvan
tages

Attenuation only
above U
VDR
Suitable for
most standard
applications,
e.g. in the
SIMATIC
environment
Advantag
es
 RF attenuation
 Well suited to AC
voltage
 Attenuation
independent of
levels
RC
elements
AC/DC According
to
dimensionin
g
 OFF-delay
remains
unchanged

Rates of rise of
voltage are
attenuated
Disadvan
tages

High inrush current

Sensitive to
harmonics
With critical
operating times
1)
The drop-out speed falls to zero once or twice for a few milliseconds:
● Safe drop-out is always ensured during current-free switching.
● When switching with a current present, the contacts are subjected to a higher thermal
load. This can lead to an overload when switching at the high current limit.