High Leg 3 Phase Question.

[WNMG442]

Hi all. I've been lurking here for a bit at the recommendation of a friend of mine who's a long time member. I recently moved my mostly 3Φ equipment including (a CNC VMC and CNC lathe) to a shop that didn't have utility 3Φ. I just installed a phase perfect phase converter and found out it produces high leg 3Φ. I understand the concept fairly well (I think) and read a couple of threads here about it, but just want to make sure I have the practical application correct as not to let the smoke out of some fairly expensive components. I have a separate 3Φ panel for these machines, with the high leg (manufactured leg) wired in orange on L3. It is my understanding that I can wire the machines as I would with delta 3Φ if I don't run/need a neutral, and so long as I make sure any transformers feeding controls or readouts are not fed by the high leg. At my old shop these machines were simply wired 4 wire with 3 hot legs and a ground. Is it a correct understanding that even though this is a different system, I'm essentially wiring things the same way? Again, only with attention needed as the what is fed by the stinger. Does this sound correct? Am I missing anything?


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[sdelivery]

This sounds correct, but I don't honestly know.
I would just disable circuits or components I am worried about until you can test.
This is normally called "commissioning "
You open up all circuits and bring each on line as you can verify voltages, polarity, equipment grounds and motor directons and e-stop circuits.

 

[mksj]

My understanding is that you are fine as long as the systems do not require a neutral to be wired to the machine, the same applies to using an RPC. If you require a neutral connection then you need a delta to wye isolation transformer. With both the Phase Perfect and the manufactured leg should not be used for control circuitry or their supply transformer. There may be an issue if the machine uses a surge suppressor or electrical noise EMG filter, as they may be referenced to ground/neutral and the voltages would be different to the generated leg. I recall that VFD's that have this integral that they can be disconnected. Surge suppressors are usually specific to the voltage reference from leg to leg and leg to ground. You may want to check with the machine manufacturer's/Phase Perfect if your machines would have any problems.