Actually, the entire concept, as you have posted it, is preposterous. So either you heard and recorded it incorrectly, or the machine manufacturer is way off base.
We can ASSUME that what they MIGHT have MEANT was that the AVAILABLE FAULT CURRENT at their machine must be 10kA or less. That seems far more likely, but is not what you posted. So first off you must get clarity on exactly what they want using appropriate terminology.
- AIC = Amps Interrupting Capacity; a term for PROTECTIVE DEVICES that will interrupt the flow of current in the event of a fault. Breakers have an AIC rating based on the maximum amount of current they can handle going through them during a fault, because UNTIL the breaker interrupts the flow of current, ALL of the AFC will be attempting to flow through it and the mechanical stresses that represents (magnetic repulsion / attraction) can literally make it explode..
- IR = Interrupting Rating. Fuses have an Interrupting Rating which is technically the same, so it's a little odd that Cooper was being so literal. But yes, technically it's not an interrupting CAPACITY I guess.
- AFC = Available Fault Current, also known as Short Circuit Amps (SCA); the term for how much fault current (typically in kA or thousands of amps) that are available at the line side terminals of something. It's derived from the transformer size, the capacity of the primary circuit of that transformer, the impedance of it and any other impedance values between that and the line terminals, typically the resistance of the length of cables (and anything like reactors added).
- SCCR = Short Circuit Current Rating; the TESTED value of a piece of equipment to withstand the mechanical forces that might take place during a fault of the rated current. This is typically a combination OF the AIC / IR of the protective device, the Let-Through current of that device and mechanical strength of the power devices down stream.
- Let-Through = the amount of current that will get through a protective device (CB or fuses) in the time it takes to stop current from flowing during a fault.
If it IS the case that what they meant was 10kA
Available Fault Current (A
FC), then their asking YOU to do something about it via component selection in the panels you installed is bogus. That's not how that would work. Attempting to limit the AFC at a machine is a tricky business and often not realistic, but is something that would more likely involve the services of a registered PE. Machine OEMs tend to not like to hear that though, they want to build the cheapest thing they can get away with and try to shift the burden off to someone else. The CORRECT way to do this would have been for them to ASK their customer what the AFC already IS, then build their control panel accordingly, along with a UL listing that showed an official
SCCR (Short Circuit Current Rating) on the label as is now required by code. After the fact is not the way to approach that issue.
