Starting on page 7, the white paper that Rich linked to also references UL 508A, supplement SB, which is a method of determining SCCR for industrial control panels without test. The method at a high level involves carrying over the SCCR rating of the "weakest link in the chain" from a protective component standpoint to the overall panel. I wonder if that method may have been used for the machinery in question, with a component level voltage rating (improperly, in my opinion) shifted over to the end device. Note that UL 508A includes "at a nominal voltage" in its definition of SCCR.
On Tue, May 14, 2024 at 12:33 PM Richard Nute <[email protected]> wrote: > > > Hi Brian: > > > > See the very last line of: > > > > > https://www.mouser.com/pdfDocs/littelfuse_industrial_whitepaper_increase_sccr.pdf > > > > Best regards, > > Rich > > > > > > > > > > *From:* Ralph McDiarmid <[email protected]> > *Sent:* Tuesday, May 14, 2024 11:41 AM > *To:* [email protected] > *Subject:* Re: [PSES] SCCR Rating Question > > > > Could this number to used to select a suitable circuit breaker and so the > interrupting voltage is an important parameter? > > > > The nameplate rating on the machine should be the information an > electrician needs during installation and selection of wire size and type. > > > > Ralph > > > > *From:* Brian Kunde <[email protected]> > *Sent:* Tuesday, May 14, 2024 11:29 AM > *To:* [email protected] > *Subject:* [PSES] SCCR Rating Question > > > > Greetings to all. > > > > I am new to SCCR ratings on industrial machinery. The ratings I have seen > sometimes has a "Maximum Voltage" included, such as; > > > > SCCR: 22kA, 600V Maximum > > > > Where does the voltage value come from? In one case, the machine had a > line voltage rating of "120/208 Vac", but the SCCR rating had a voltage > rating of "Max 600V". > > > > Can this be confusing? Might something think the machine can operate at > 600Vac? > > > > Thanks for any replies. > > The Other Brian > > > > > ------------------------------ > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. 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