Siemens NEC Article 409 - Basic Steps for Calculating the SCCR of a Control Panel; SB4.2 - Determining the Short-Circuit Current Ratings (SCCR) of Individual Power Circuit Components; Basic: Device Markings or Component Instruction Sheets

Short-circuit current rating (SCCR) of industrial control panels
Reference Manual, 06/2013, A5E31896849002A/RS-AA/001
13
Basic steps for calculating the SCCR of a control
panel
4
4.1
SB4.2 – Determining the short-circuit current ratings (SCCR) of
individual power circuit components
The short-circuit strength of individual power circuit components can be calculated using
three possible methods:
● Based on device markings or component instruction sheets
● Based on assumed short-circuit current rating
● Based on tested combinations of devices according to UL508
4.1.1
Basic: Device markings or component instruction sheets
Most Siemens power control and circuit protection components include a standard short
circuit rating on the front or on the nameplate.
Example of marking on a 3RT contactor
Figure 4-1 Nameplate
Exception
The short-circuit current rating of Siemens frequency converters is stated in the operating
instructions or the relevant catalogs. This complies with the requirements of NEC Article 409
and is therefore entered in the relevant UL test reports.
Moreover, in the case of frequency converters that are protected with fuses, circuit breakers
according to UL489 or self-protected combination motor controllers per UL508 type E, the
short-circuit current rating of the drive in conjunction with the line-side protective device is
stated.