Re: [CAD_CAM_EDM_DRO] Re: Motor calculations? Help!

/// By the data provided, they are 24.3 in-lb motors 11.5 amps continuous. Need at least 3:1 reduction for X and Y, forget driving the knee(if it's a Bridgeport). Calculating above the continual rating is irrelevant. At 20 amps my 40.5in-lb 13 amp continuous servos would be 62.3 in-lb. Running fine on Geckos. His will run on Geckos no problem with reduced RPM due to the voltage restriction. The best way to protect the motors/drives running larger servos is to design the power supply with a Kva rating close or slightly above to one of the servo's continual amperage at the drive's restricted operating voltage.

Ron
///



Lance Hopper <snaggletto@...> 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"
wrote:

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson

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

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