Re: Motor calculations? Help!

I believe he is referring to the secondaries of the transformer when
he indicates 120v. Presumably the primaries are for 208/220/440 or
similar.

Pete C.

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> wrote:
> Lance Hopper 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.
> >
> >
> Ah, OK, that sounds like the best course.
>
> > 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?
>
> No, it really will not work well on single phase. Where did this
thing get
> 120 V 3-phase power? That is an extremely odd voltage. 208 and
230 V
> L-L is the most common low-voltage 3-phase supply in the US. Or,
is this
> 120 V line-neutral voltage? That would normally be termed 208 V 3-
phase,
> as the line-line voltage is how it is usually measured.
>
> > 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?
> >
> The best way to go, I think, would be to use a 240:120 V step-down
> transformer
> rated for 2.5 KVA at that voltage. (If you can't find one with
that
> exact rating,
> you could use a 480:240 V 5 KVA transformer at half input voltage.)
> With a 240 V output with a center tap, and using 2 diodes, you can
get
> 170 V DC, which may be acceptable to the Rutex drives. (I'm being
cautious
> here, because the Rutex's 200 V rating is apparently the actual
rated
> voltage
> of the transistors. So, I don't know if the 200 V Rutex drive can
> actually be
> run off 170 V DC without problems. It is probably best to ask
Rutex about
> that. If necessary, one can get tapped autotransformers to adjust
the
> voltage down somewhat.
>
> Jon
>
> >
> > 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
> >>
> >>
> >
> >
> >
> >
> >
> >Addresses:
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