Siemens NEC Article 409 Reference Manual page 21

4.2 SB4.3 – Adaptation of the available short-circuit current rating based on the peak let-through currents when
using current-limiting devices in the feeder circuit
Examples
The following two examples show a fuse as the feeder circuit protective device. The
procedure described also applies if a circuit breaker according to UL489 is used as the
feeder circuit protective device.
Example 1
⇒ SCCR 35 kA since the circuit breaker is only suitable for 35 kA.
The contactor and overload relays are protected by the fuse in the feeder circuit since 5 kA
(SCCR of contactor and overload relays) is > 3 kA (let-through value of the fuse).
Short-circuit current rating (SCCR) of industrial control panels
Reference Manual, 06/2013, A5E31896849002A/RS-AA/001
Basic steps for calculating the SCCR of a control panel
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