Configuration
6.9 Switching of capacitive loads
SIRIUS - SIRIUS 3RT Contactors/Contactor assemblies
112 Manual, 09/2017, A5E03656507120A/RS-AE/006
Note
Recommendations for configuration/operation:
•
Use the recommended conductor cross-sections only
Avoid connecting leads that are too short
Wire capacitors with discharging reactors instead of discharging resistors to avoid
energizing of still charged capacitors in the event of a disruption of the control voltage.
Prevent manual operation of the capacitor contactors under load voltage. This can lead to
destruction of the precharging resistors and to welding of contacts.
Implement circuitry measures to ensure compliance with the required idle times after
deactivation or short-time interruption of the control voltage. Inadmissibly short idle times
or inadmissibly high switching frequency can produce overloading of the integrated
precharging resistors or welding of the contacts if the necessary discharging time of the
capacitors is not observed.
Check connection terminals at least once every year for preserved clamping force and
retighten them, if necessary.
Observation of the effective capacitor current for a period of 24 hours is recommended so
as to be able to ensure that the permissible average current load of the contactor's
current paths (1.3 x Ie AC-6b) is not exceeded.
Measurement of the harmonic component of the capacitor current is recommended. If the
rms value of the current downstream of the supply transformer, or a proportional
converter load, is higher than 20 % then suitable measures must be taken (connection of
reactors to the capacitors, or installation of filter circuits).
To avoid jeopardizing systems and persons, defective capacitor contactors are not
permitted to be repaired.
The minimum idle time is derived from the maximum switching frequency as follows:
Maximum switching frequency
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