Re: [CAD_CAM_EDM_DRO] Re: VFD for a 15HP CNC lathe

----- Original Message -----
From: "caudlet" <info@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, October 26, 2003 6:37 AM
Subject: [CAD_CAM_EDM_DRO] Re: VFD for a 15HP CNC lathe


> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "fuddham" <fuddham@a...>
> wrote:
> > I have a CNC lathe that has a 15 HP spindle motor. What size VFD
> > would I need if I only fed the VFD single phase power? Would it be
> > better to get a 15 hp VFD and use a rotary phase converter to feed
> > the VFD? What size VFD and Rotary converter?
> >
> > Thanks,
> >
> > Scott Hamilton
>
> 15HP! Now THAT's a CNC lathe!!
>
> Scott, 15HP VFD's get pretty pricey. Most of the solid state ones
> are rated for 1 to 5 HP. On a lot of the older VFD models the HP
> rating is with 3 phase in, and they have to be derated 50% for single
> phase in. That motor probably draws 35A @ 230VAC and 10 times that
> amount on startup for a few seconds.
>
> A rotary converter would make more sense in this case. You need one
> rated for at least the 15HP. One of the nice things about rotary
> converters is that every 3 phase motor you put on the "grid" actually
> helps stabalize it and becomes part of the generator. You have to
> have enough 3 phase to start the first motor. If it is not loaded
> then it becomes a secondary generator and you can start a bigger
> motor (etc, etc). There are plans on Metal Web News on how to build
> your own 3 phase rotary converter. Used Large 3 phase motors are
> usually pretty cheap and you can find the caps involved surplus on
> the web. Don't waste your money on the static converters.
>
> Tom C.
>
>
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