Operating the contactor panel with panel width 435 mm
110-0134.9 / 14 NXAIR / ≤ 40 kA 147
• The selected HV HRC fuse-link limits the sustained symmetrical short-circuit current I
K
to the let-
through current I
D
, shown in the diagram for the current-limiting characteristics (I
D
as a function of I
K
for HV HRC fuse-links with different rated currents). The maximum permissible let-through current is
I
D
= 46 kA.
Requirements
The coordination of the components of the motor circuit requires the following:
• The let-through current I
D
must not exceed 46 kA at 7.2 kV/12 kV.
• In case of low-voltage supply via a control transformer, short-circuit currents ranging above the limit
breaking capacity must be interrupted within 80 ms. This requirement does not apply if
• the mechanical latch is provided.
or
• the opening times have been extended so much that – in the a.m. current range – the contactor
can only open when the fuse-link has interrupted the current.
• Due to the arising motor starting current, the instant when the motor starts represents the maximum
stress for the HV HRC fuse-link. This stress must neither operate nor pre-damage the fuse-link.
• Other factors of influence on the stress of the HV HRC fuse-links are the starting time and the
starting frequency of the motors.
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