Eaton Logo

How can the short circuit current rating (SCCR) of control panel be calculated based on UL508A Supplement SB

There are three simple steps to calculate the SCCR (Short Circuit Current Rating) of a control panel.

1) Determine the individual short circuit current rating of each individual component in the system. All power circuit components, including disconnect switches, branch circuit protective devices, branch circuit fuse holders, load controllers, motor overload relays, terminal blocks and bus bars, shall have a short circuit current rating expressed in amperes or kilo amperes and voltage. Panel builders can exclude transformers, dry-type capacitors, resistors, varistors and voltmeters.

 

2) Calculate the available short circuit current when taking into account current limiting components like control power transformers, fuses and circuit breakers.

 

3) Compare the values obtained in steps one and two to determine the overall short circuit current rating of the panel. The lowest rated SCCR of the device within the control panel must be the one that is marked on the panel.

 

I need the SCCR, short circuit current ratings for electrical components