Senior Member
Saint Louis
Hey Everyone,

I'm working on a power systems study that won't die. I completed this project about a year ago and the owner is coming back and asking me to furnish labels for equipment that is not in the scope of work. The contractor just asked if I can provide labels for an inverter so they can get off of the commissioning log and get paid. I think I can model inverters in SKM power tools, but I don't have the DC systems analysis. My question is: Has anyone ever modeled an inverter in SKM power tools and has anyone been asked to provide a arc flash label for an inverter before?

Best Regards
NEC (in simplified terms) says you only need labels for equipment that will undergo maintenance or servicing while equipment is live. In what case would you need this inverter to be worked on live? UPS have an inverter built-in, but in most cases the are also paralleled with a maintenance by pass. Id double check the code and your oneline to make sure its needed. 110.16


Senior Member
Rutland, VT, USA
Electrical Engineer, PE
For the inverter, it should be labeled with the worst case incident energy value which will most likely be from the AC source. Typically an inverter will have protection to shut it down quickly to protect the sensitive and expensive electronics. Usually the inverter will shutdown on 10% above FLA.
There is a table in NFPA 70E for DC systems PPE and in Annex D, the maximum power method is shown for DC incident energy.