Have a friend that may be looking for one to convert single to 3 phase.


--
Greg O

On 2009-11-21, Greg O wrote:
Have a friend that may be looking for one to convert single to 3 phase.

No, and you would be hard pressed to find something other than full
new price at driveswarehouse.com. Drives in this size usually have a 3
phase fault sensing circuit. Good luck looking.

A big phase converter may be a better bet, price wise. Used 3 phase
motors go for $5 or so per HP at scrap yards. So you are looking at
$150 in motors (say, three 10 HP electric motors) and an additional
amount for doodads like caps and starters, if you want to build a RPC
with 30 HP idler capacity.


i

On Fri, 20 Nov 2009 23:50:47 -0600, Ignoramus29320
wrote:

On 2009-11-21, Greg O wrote:
Have a friend that may be looking for one to convert single to 3 phase.

No, and you would be hard pressed to find something other than full
new price at driveswarehouse.com. Drives in this size usually have a 3
phase fault sensing circuit. Good luck looking.

A big phase converter may be a better bet, price wise. Used 3 phase
motors go for $5 or so per HP at scrap yards. So you are looking at
$150 in motors (say, three 10 HP electric motors) and an additional
amount for doodads like caps and starters, if you want to build a RPC
with 30 HP idler capacity.


i

Sorry to gloat (no I'm not :-), but my 23HP VFD cost me £10. Doesn't object to
working 1ph in, 3ph out. I use it with a step up transformer to go from 240V
single to 415V three phase. I'm not often lucky, but I scored on this oneBEG


Mark Rand
RTFM

Greg O wrote:
Have a friend that may be looking for one to convert single to 3 phase.


You may not find such a unit, period. The larger
VFDs, up in this range,
often have phase-loss detection, and will power on
and show an error
code when run on single phase. If you do find one
that will operate, it
may have a short life. You can get away with
playing these tricks with
smaller units, and I do it myself, but it gets
messier as you go up in
size.

Is this for a 20 Hp motor, or are you already
derating it for a 10 Hp motor?
A 10 Hp motor will draw about 8500 pure Watts.
Adding a little loss for
the VFD, you will draw maybe 9 kW, or 37.5 A at
240 V. Adding another
factor for power factor, you will draw over 40 A,
that's a lot on a 240 V
service.

Also note that you can't run ANYTHING other than a
motor off a VFD,
such as a welder, CNC or whatever.

If you need to run a 20 Hp motor off residential
240 V single-phase
service, I hope I'm not in your neighborhood.
You'd need an even
bigger VFD, and line current would approach 100 A.

Jon

"Jon Elson" wrote in message
...

Is this for a 20 Hp motor, or are you already derating it for a 10 Hp
motor?
A 10 Hp motor will draw about 8500 pure Watts. Adding a little loss for
the VFD, you will draw maybe 9 kW, or 37.5 A at 240 V. Adding another
factor for power factor, you will draw over 40 A, that's a lot on a 240 V
service.



I have a friend looking to run a 10 motor on a Causing lathe. He is planning
on a rotary converter, but would consider a VFD if a deal on a used one
could be found.
Greg