Re: [CAD_CAM_EDM_DRO] Re: Three Phase Power

jeffalanp wrote:

>Hi Jon (et. al.),
> I was concerned that I would get a large amount of ripple on the
>capacitors that create the DC buss in the VFD (which 'wants' three
>phase) if I only used single phase, isn't this true?
>

Yes, it is true. But, the capacitor banks in the drives are REALLY
large, to tolerate momentary
power dips. My 1 HP VFD, running on single pahse, and driving a 1 HP
Bridgeport motor, will
hold up for at least half a second while running the motor without
tripping! I know, because it
got REAL dark in my shop one night, and I had time to reach behind me
and start feeling for a
flashlight before the lights came back on again. The VFD and the rest
of my CNC system
kept cutting right through it without a blip! (And, I don't have a UPS
on any of it.)

> Using three
>phase would reduce the rectified ripple to almost nothing. Should I
>just add some extra BIG caps to the DC buss on the VFD if I use
>single phase (or is feeding single phase to the VFD really not as
>much of a problem as I though it might be)?
>
>

The capacitor bank will have its life reduced slightly. But, these
things are usually designed to
run in still air at 45 C, so if yours is in a cooler environment than
that, it will not really affect
life. Bigger caps may cause the current surge in the rectifiers to be
worse, too.

Jon