240VAC/120VAC service and EMI filter questions

[philba]

This is more of a code question, I think. I'm putting together the controller box for a 48x48 router and will be running most of the power supplies from 240VAC (nominal). I have my shop wired for 240V/40A with a neutral line as well. I will be using a 240VAC EMI filter for the VFD and a separate one for the electronics cabinet. I plan on an unfiltered power supply for the steppers - maybe 80VDC output with 240VAC input. I will need 120VAC supply for some equipment (power supplies, pumps, fans, lights and such). I expect that draw to be 1-2A max. Dust collector will be supplied from a separate circuit though switched by the controller.

The questions:

• Is having 2 EMI filters overkill? Not super expensive so I don't mind and I worry about the VFD "polluting" the stepper PS if they share input power.
• How much larger should my EMI filter current rating be over the likely draw? I'm thinking at least 20%
• Is it a US NEC code violation to run a power cord to a distribution box (ie 2 outlets) for 240VAC. I was hoping to put the EMI filters there.
• Can I take the 120VAC draw from one of the 240 legs and neutral? I know I can but is that US NEC code compliant?
• Do I need to balance 120VAC draw on both legs of the 240VAC circuit?

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[Al_The_Man]

There is no need to 'balance' each 120v circuit.
You should however have a valid distribution method, not fed from two 120v outlets, you should have an enclosure that distributes the 120- 0 -120v to each of the circuits, properly fused.
As to EMI filters on the VFD, the VFD has a natural filter immediately the supply enters it, this consists of a 3ph rectifier feeding a very large capacitor bank.
If using a ordinary 240v 3ph motor, you are better off to put the money into a 3ph choke on the VFD output.
It is best to consolidate everything in one enclosure rather than a mish-mash of separate devices hooked up.
BTW, when wiring, it is not code to use a wire gauge that has a larger fuse or protection than the conductor rating.
Al.

[philba]

Thanks, Al. It is a real 240VAC line, not 2 120s.

I've got this on the way. [edit: fixed link]

And, yes, no point in using a fuse that doesn't protect the wire.

[Al_The_Man]

Link did not work for me!

[philba]

Link did not work for me!

works for me but I edited it with a different link, maybe that will work.