CB-110-4 25
VARIPACK frequency inverters fulfil the requirements
for THC (table 3) of EN61000-3-12 without the need for
external line reactors provided that the short-circuit
power S
SC
is greater than or equal to S
SC (min)
at the in-
terface point of the network operator. It is the respons-
ibility of the installer or user of the equipment to ensure
this.
Calculation:
S
SC (min)
= 320 × V
rated
× I
rated
Where V
rated
is the drive rated voltage (phase to phase)
and I
rated
is the drive rated current (per phase).
This corresponds to an R
sce
> 185 according to
EN61000-3-12, table 3.
5.10 Safe Torque Off (STO)
As standard, the VARIPACK frequency inverters are
equipped with a shut-off function, the Safe Torque Off
(STO). Due to the STO function, the main contactor be-
fore or after the VARIPACK frequency inverter may be
omitted.
Responsibilities
The overall system designer is responsible for defining
the requirements of the overall “Safety Control System”
within which the FI will be incorporated. Furthermore
the system designer is responsible for ensuring that the
complete system is risk assessed and that the “Safety
Control System” requirements have been entirely met
and that the function is fully verified. This must include
confirmation testing of the STO function before FI com-
missioning.
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