Re: [CAD_CAM_EDM_DRO] Re: Transformers 3 phase power calculations and fuse size

On Monday 25 April 2005 08:49 pm, Pd62448@... wrote:

> Hello in this group. Thanks for the referral. I have been reading
> the archives.....but there are over 80,000 of them. My question is more
> basic than any responses I have found. I have a Bridgeport Series I CNC
> with a Machine Master aftermarket controller that was allegedly running
> when removed from service. I can't get three phase at my shop. I have a
> VFD for the spindle, and all other transformers are single phase. The
> power transformer for the steppers is obviously three phase. My questions
> are:
>
> !.) Can I replace the three phase transformer with an equivalent single
> phase unit without changing anything else downstream? Or is there
> something unique about this transformer because of it's phasing? If it's a
> straight swap can I get a suggestion for size?

The major difference to the stuff "downstream" is going to be a significantly
higher ripple on the DC output, so you might want to add some more filter
caps.

> 2.) Would it be better or easier or significantly cheaper to just run a
> rotary phase converter ahead of the whole machine (less the VFD and
> spindle)? This doesn't seem like a very elegant solution but I am not
> electronically gifted. I am struggling to get up to speed in the archives
> but would ask everyone's indulgence with the elementary nature of my
> questions. I think I can learn more if my machine is running.

The biggest problems with using a rotary converter is two things: One is the
fact that they're mechanical, and therefore subject to wear in ways that
electronics aren't, and the other is that they're not very efficient.