Welding Receptacles Delta Ungrounded Transformer

[killer76]

I have installation issues needing code advice, suggestion or perhaps provide location in the code that may permit this application.

Multiple 1PH and 3PH receptacles set up for mig / tig welding machines and a few plasma cutters.
60A fused disconnect w/ 50A fuses wired to (2) 1PH 30A receptacle #10awg, and (1) 50A 3PH #8awg x 10’ SO cable receptacle plug.

I believe is safest approach 630.13 a single fused disconnect for each plug/welding machine, (only one of the machines has an integral disconnect)

Looking at 630.11 (B) unit duty cycle for group Arc welders may not apply as none are Arc welders, or do these machines apply.

The receptacle supply from 112.5kva 480X240 3 PH DELTA to 225A 3PH load center. Disconnect wired #8awg X200’ voltage reading L-L=V, L-G=0

Should the transformer be corner grounded? Or install ground detection system 250.21

Thank you

 

[zbang]

I'm not up on welders specifically, but unless there's an exception in Art. 630 you're not allowed a 30a receptacle on a 50a fuse. I'd go with single fused disconnects (which could be lockable breakers) per receptacle.

If this is an existing supply, it should already be grounded/bonded appropriately (but in most cases, corner-grounded is preferable to un-grounded with a detector).

 

[killer76]

It was explained that because the machines are an inverter type of unit more than one receptacle could be connected to the same disconnect.

I can only suggest they install an individual disconnect for each machine, then refer to the manufacture installation guild lines on the OCP for each specific machine.

Corner grounding Delta 240 3PH, reading posts about this refer to 240.22 that permits OCP on the grounded conductor, if condition (1) is met.

Would the fused disconnect be acceptable if they are they are supplied from an individual breaker in the panel.

Thank you