ANSI vs IEC current ratings for MCC, SWG, etc? 1

[Dvhez]

I'm currently working on oneline diagrams and I need to determine the current rating for the horizontal bus in motor control centers, switchgears, switchboards, etc. Which reference should I consider in order to write a voltage/current/short-circuit rating which is commercially available?

For example, for Motor Control Centers in ANSI world I was looking the NEMA ICS 18-2001 (R2007) which says in chapter "4.3 Continuous-Current Ratings of buses":

The horizontal common power bus shall have a continuous-current rating of 600, 800, 1000, 1200 amperes or higher as required by a particular application. Vertical bus extensions installed in a section shall have a minimum continuous-current rating of 300 amperes.

 

[jraef]

If the MCC is going to be sourced and used in North America (and places influenced by NA), use the NEMA ICS 18/UL 845 ratings. IEC means nothing here. If it is going to be used outside of North America, then stick with IEC standards. If it will be sourced in NA but used elsewhere, most NA MCC mfrs have an IEC designed MCC available, but they will not be UL / CSA listed. If the MCC will be sourced overseas and used here, that's more difficult to get done, you are better off sourcing it here.

Pretty much the same will hold true for switchgear.

In NEMA MCCs, fairly universally available ratings are 600, 800, 1000, 1200, 1600, 2000 and 3000A main horizontal bus, but at 3000A you start running into all kinds of catches and restrictions. Vertical bus will be 300A or 600A. Bus bracing options are typically 42kA, 65kA and 100kA, although I think a few suppliers might still offer a 25kA option (I wouldn't go that low however).

Switchgear / switchboard / panelboard bus ratings are more diverse and depend on which type of equipment you are talking about.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[cuky2000]

See the enclosed links associated with ANSI & IEC Std

https://www.eaton.com/content/dam/e...or-MV assemblies-the-Brazilian-experience.pdf

https://new.abb.com/docs/librariesp...-gretler---ansi-vs-iec-apw-chile.pdf?sfvrsn=2