Accessories
9.4 Surge suppressor
SIRIUS - SIRIUS 3RT Contactors/Contactor assemblies
Manual, 09/2017, A5E03656507120A/RS-AE/006
305
RC circuit with suppression diode
Including a diode in an RC circuit ensures that switching overvoltages will no longer occur;
the diode limits the voltage to 0.7 V.
Note
However, diodes extend the OFF delay (break time) by a factor of
6 to 9. This characteristic
can be turned to the user's advantage if brief
voltage dips in the range of a few milliseconds
example. Freewheeling diodes are only technically useful for size
S00 contactors. For higher power ratings we recommend an RC circuit with a diode
combination.
Figure 9-11 RC circuit with diode (DC operation)
Advantage: No overvoltages occur during the switch-off process. The diode blocks at 0.6 V.
Disadvantage: The diode can only be used for DC operation. The contactor's break time is
extended considerably, amounting to 6 to 9 times the switch-off delay. This longer break time
can be used for control purposes if required, e.g. to bridge short-time voltage dips.
Diode combinations are available for shorter break times.
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