Re: [CAD_CAM_EDM_DRO] 5HP VFD

I believe that some of the previous posts are correct concerning the
application of a three phase VFD to a single phase line. A three phase
VFD is theoretically capable of operating on single phase since the
incoming power is immediately rectified and then inverted to supply the
three reconstructed line phases at the appropriate frequency. The
obivious problem problem is that the single phase input cannot supply
the same power (watts) as three phase input drawing the same current
(amps). This is illustrated by an Allen-Bradley 1HP 160S VFD drive. The
drive requires 9.4 Amps Single Phase at 220VAC to supply 4.5 Amps Three
phase also at 220VAC. The extra power cannot just be created it must
come from a higher current draw on the single phase line, hence the need
to derate the drive.

The practical issue however is that many or most VFD are phase loss
protected to prevent their operation in case one leg goes low. The phase
loss would reduce the incoming power to the DC Buss and greatly reduce
the capacity of the drive to supply the driven motor most likely
resulting in a motor stall. As a result, while the drive could operate
in a derated mode on single phase, its "intelligence" tells it "THIS
AIN"T RIGHT", inhibits operation and flashs an error. Could you preform
a lobodomy on the drive and make it "dumber"? Maybe, but it would be
have to be done by someone smarter than I am.

I believe that the primary difference in a VFD rated for three phase
input verses single phase input is:

a) The single phase DC Buss is derated significantly to compensate
for the lack of the power that would be derived from the two missing phases.
b) The single phase Drive Logic either has the phase loss protection
disabled for a drive such as an Allen Bradley 160S and setup for single
phase only or the logic is Auto-Sensing to detect the presence or
absence of three phase and operate accordingly like the Mitsubishi
drives. I currently use both and have found both to be "bullet proof"
even when abused. They will take a licking and if parameters are
exceeded they either go into current limit or warn you before shutting down.

nitewatchman





Jon Elson wrote:

> Vince Endter wrote:
>
> >I am looking for a 5HP VFD that will take single phase input.
> >Automation directs drives stop at 3hp with single phase.
> >
> >
> >
> If you are not going to max it out in a home shop environment, then almost
> any 5 Hp VFD will work. These things are rated to run for 5-10 years, flat
> out, in a 50 C equipment cabinet. Using it intermittently, at less than
> full rated power, in a 25 C environment, it should handle it fine. I
> have used
> a 1 Hp drive rated for 3-phase input only on a 1 Hp Bridgeport, and it
> has not
> caused any problem at all. I've been using it for something close to 10
> years,
> now!
>
> On the other hand, if it is for air compressor duty, for instance, then
> I would
> definitely go to a larger size VFD, say a 7.5 Hp model.
>
> There are a few new models turning up that have lost phase protection.
> Maybe we should start a list of drives known to work on single-phase
> power,
> and those known to shut down if they don't see 3-phase.
>
> Jon
>
>

[Non-text portions of this message have been removed]