Re: Motor calculations? Help!

A three phase transformer is more-or-less three single phase
transformers. They don't blow up if you loose a phase although the
equipment you have connected to them might.

Using one or two sections of a three phase transformer in a single
phase configuration might reduce the efficiency slightly, but should
not be dangerous.

As long as you're not trying to exceed any of the ratings of the
transformer it should be ok. You won't be able to get 2.5kva total
out of 1/3 or 2/3 of the transformer of course. The main thing is to
make sure you have the windings configured appropriatly for what you
are trying to do.

Pete C.


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Lance Hopper"
<snaggletto@c...> wrote:

>
> Hello,
> I've been talking to the guy myself trying to help him out.

He's

> already bought 200V 40A Rutex drives as I understand. Now he's
> trying to figure out the PS.
>
> The original drives were fed 120 3ph from the secondaries of a
> 2.5kva 3ph transformer as he describes via his electrical

schematics.

> He was trying to see if the stock 3ph transformer (has delta and Y
> wiring configurations, he has the schematics, maybe he should post)
> could take ~220 1ph (all he has available) and output ~120 1ph that
> could be rectified and used for the Rutex drives. I doubted that

it

> would work and be dangerous/stupid to try, but what do I know.
>
> Is there any way to use a 3ph transformer for 1ph in and 1ph

out?

> What if he used a phase converter and ran 220 3ph to the primary,
> then just ditched one of the 120 3ph legs to get 120 1ph to be
> rectified/filtered for the Rutex drives? Any safe/smart

workarounds

> on this?
>
> Otherwise, he's going to have some $ into some large kva
> transformers for the X/Y and Z servos.
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "cnc_4_me" <cnc4me@g...>
> wrote:
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...>
> wrote:
> > > cnc_4_me wrote:
> > >
> > > >Jon, I do not see this the same way you do. Don't you think

the

> > > >continuous current rating is more important than the peak
> current
> > > >rating? 28 Kg-Cm / 2.44 Kg-Cm/Amp = 11.5 amps, a gecko would
> > still
> > > >have plenty of reserve. 20 amp limit would still give 49 Kg-

Cm.

> I
> > > >wish i had one of these motors for my Z axis.
> > > >
> > > >
> > > What's the peak rating for, if you never can get closer than

20%

> of
> > it?
> > > I might be worried that you might not be able to break static
> > friction on
> > > the table with 20 A. What is the leadscrew pitch, and is the
> screw
> > directly
> > > driven by the motor, or is there a belt reduction?
> > >
> > > What horsepower and spindle taper does the machine have?
> > >
> > > Jon
> >
> > From what I understand from reading these forums is that any

force

> > much greater than continuous rating isn't to usable, maybe for a
> > fraction of a second for fast acceleration. Maybe if he adjusts
> > acceleration so it does not snap your eyeballs it would be ok.
> >
> > 49 Kg-Cm is about 47 lb-in. Nothing to sneeze at.
> >
> >
> > I guess what I am getting at is I would not try to discourage

this

> > guy and say it will not work. I think it is very likely it will
> > work with slower acceleration and with 30% less speed on X and Y
> > because of voltage restrictions with Gecko drives. Rutex would
> give
> > him full speed and slightly higher acceleration.
> >
> >
> > Wally