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Switching overvoltage - surge suppressor
Overvoltages when switching off contactors (inductive load) can cause faults in electronic
devices (timing relays, PLCs, coupling modules) in the same network if the contactors are
used without the appropriate filters.
Table 9- 18
Switching overvoltage - surge suppressor
Description
Suitable
for
Freewheel diode
DC
Suppressor diode
AC/DC
Diode
DC
combination
Varistor
AC/DC
RC element
AC/DC
SIRIUS - SIRIUS 3RT Contactors/Contactor assemblies
Manual, 09/2017, A5E03656507120A/RS-AE/006
Limited to
Additional delay
Forward voltage
Very high (6-9x)
(U
= ~1 V)
D
Breakdown
Very low
voltage (U
)
BR
Breakdown
Very low
voltage (U
)
BR
Varistor voltage
Very low
(U
)
Varistor
U
Very low
RC
Advantage
Non-critical
•
dimensioning
Lowest induction
•
voltage
Very simple and
•
reliable
Low-cost
•
Non-critical
•
dimensioning
Simple design
•
Protected against
•
reverse polarity
Short pick-up time
•
Non-critical
•
dimensioning
Simple design
•
Short pick-up time
•
Non-critical
•
dimensioning
High energy
•
absorption
Very simple design
•
HF attenuation
•
through energy
storage
Immediate shutdown
•
Extremely suitable for
•
AC
Accessories
9.4 Surge suppressor
Disadvantage
Long drop-out
•
delay
Short-circuit on
•
failure
No attenuation below
the breakdown voltage
(U
)
BR
No attenuation below
the breakdown voltage
(U
)
BR
No attenuation below
U
Varistor
Exact dimensions
•
required
Expensive
•
299
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