480 is an area where many extra rules/precautions are required. I'd skip
While I understand that the US NEC article 490.2 defines the border
between LV/HV at 600 V, However, I was not able to determine, if this
is phase to neutral, phase to phase, RMS or peak or even peak-to-peak
and does it apply to DC also ?
Traditionally, three phase voltages are specified line-to-line RMS.
Dunno about DC, or about the use inside a machine (as AC or DC), but the
main concern is arc flash.
I don't think 240V can really flash over. Haven't seen an example before.
Don't know if it's something about the physics, if a certain amount of
voltage is required to support a plasma dense enough and wide enough that it
grows without bound, or if it's just the extra short-circuit current
available.
I do know that domestic 240V circuit breakers and fuses are rated for 10kA
clearing; 480V are required to clear 100kA and up.
The practical issue is: does the machine conform to NEC and NFPA
regulations? (Or the equivalent CE, IEC, etc. in other countries.)
And what most of those rules come down to is, as long as you have the fuses
rated for 480V duty (they're more expensive, even the smallest are $10
each), and/or breakers to clear it, and sufficient clearance and protection
on the wiring, you're fine.
Ultimately, what you do inside a box, as long as it's properly fused, isn't
too important -- having that fuse at the input is what makes it safe.
The 277/480 Vrms (Y/Delta) feed is well below 600 V. In a simple 6
pulse rectifier the rectified DC voltage is only 580 Vdc.
My experience has been 700VDC open circuit, maybe 620-650 under load (light
filtering, PF > 0.93). Big caps will draw spikier current (PF < 0.9) and a
slightly higher voltage, which might be important in VFDs.
In Europe, the IEC definitions are used, dividing between LV/HV is
1000 Vac RMS and 1500 Vdc. Thus the ordinary 230/400 V feed as the
quite common 690 V (Delta) for big motors fits well within the LVD (LV
Directive) and VFDs for these voltages are widely available.
Yeah, 400/480 is in that uncomfortable range where it's still technically
"LV", but it likes to flash over and burn or kill people, so you have to be
more careful around it.
480V 3ph is approximately 1 HP per amp (1 HP ~= 3/4 kW), and the human body
can only put out maybe 300W peak mechanical power. It doesn't take many
amperes at 480 to overwhelm what the human body can resist (mechanically or
otherwise).
Tim