Re: [CAD_CAM_EDM_DRO] 5HP VFD

gary wrote:

>The practical issue however is that many or most VFD are phase loss
>protected to prevent their operation in case one leg goes low.
>

It has bee the "rule" that drives under 15 Hp never had phase loss
protection.
I have worked with dozens of them, and never run into this before.
Lately, some
people are saying that a FEW specific models of small 3-phase input drives
now sense a missing phase and won't operate. I argue that most under-15 Hp
drives still do NOT have such sensing.

> 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.
>

Actually, that does not happen. What DOES happen is the rectifier and
capacitor bank
run much hotter on single phase. Especially on drives rated to operate
from 208-230 V
mains, the average voltage on the capacitor bank when running off 240 V
single phase
is still higher than it would be from the 208 V line.

> 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.
>
>
>

On some drives, this can be accomplished by strapping one of the
incoming lines
to two of the 3 terminals.

>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.
>
>
>

Really, it is a lifetime thing. The life of the drive will be
compromised by running at
near full power for long periods from single phase power. So, if you
are running the
drive 24/7 you definitely don't want to do this. But, in the typical
home shop, with
a couple hours of lighter use a day, the drive will probably last longer
than it would
on 3-phase in the industrial environment.

Jon