Siemens SIRIUS 3RT - Page 301

Accessories
9.4 Surge suppressor
SIRIUS - SIRIUS 3RT Contactors/Contactor assemblies
Manual, 09/2017, A5E03656507120A/RS-AE/006
301
Surge suppressor
Suitable
for
Control
voltage
Overvoltage
is limited ...
Effect
Advantages/disadvantages
Preferred
application
RC
elements
AC/DC According
to
dim
ensioning
• OFF-delay
remains
unchanged
• Rates of rise
of voltage are
attenuated
Advantages
• RF attenuation
• Well suited to AC
voltage
• Attenuation
independent of
levels
With critical
operating times
Disadvantages
• High inrush
current
• Sensitive to
harmonics
Suppressor
diode
AC/DC Breakdown
voltage U
BR
• Rate of rise of
the voltage is
not reduced
• Additional
drop-out
delay is too
low
(1 to 5 ms)
Advantages
• Non-critical
dimensioning
• Simple design
• Protected against
reverse polarity
• Short pick-up
time
Suitable for
most standard
applications,
e.g. in the
SIMATIC
environment
Disadvantages
• Attenuation only
above the
breakdown
voltage U
BR
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.