Re: Transformers 3 phase power calculations and fuse size

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Pd62448@c... wrote:

>
> Wally,
> 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?
>
> 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.
>
> TIA Phil Dorothy

I think there is more to it than just changing out the transformer
from 3 phase to single phase. Usually rectification after the
transformer takes advantage of the 3 phase power and uses 6 diodes on
the secondary to make DC. A single phase transformer would have to
put all current through 2 diodes probably overloading them. You
would have to find part numbers on diodes and find specs to know for
sure. If you get a part number post it here, we can probably find
the spec for you and advise.

Otherwise you would have to make your own power supply only being
able to use the old capacitors.

A rotary phase converter may work, I have no direct experience. Has
anyone in the group ran a 3 phase transformer off of a rotary phase
converter before.


Wally