Transformer question Wye/Delta

[kentucker237]

I recently bought a used SWI Prototrak DPM mill for my garage. This particular mill requires 440VAC 3 phase power. There is no separate power entry for 115VAC to power the electronics; all 115V power is handled by a small internal transformer. My garage has 240V single phase power. I am planning on building a 7.5 hp RPC. The manual specifies 5KVA for RPC. Fine so far.

I have found a 3 phase transformer that I want to wire in after the RPC (I’ll keep the RPC at 240VAC). Below is a picture of the ID plate on the transformer. I need a multi tap transformer that can output close to 440V with 240V input. I just don’t understand the impact of the Wye/Delta wiring. It appears that the Wye is on the low voltage side.

I’ve also posted a picture of the power entry in the electrical cabinet of the mill. As you can see, there are 3 hots and a ground; no neutral.

My question:
Will this transformer work as I need? The Wye thing has me stuck. Should I hold off and find a transformer that is Delta/Delta? Thanks for the help.

[Al_The_Man]

I would look closer into the 440 requirements, it is very likely that this is only required for any 3 phase motors, which upon inspection, may have the option to reconnect for 240.
The control power, or other 1 phase power in the machine is most likely either 240 or 120 1 phase.
The wire gauge for the the motors at lower voltage may be ok, only the fusing and over loads may need adjusting or replacing.
This would be a better option than installing a transformer.
Al.

[kentucker237]

Al, Thanks for the quick reply. These mills ordinarily have separate power entry for 3 phase to the spindle motor and 115VAC single phase for the electronics, servos, etc. This particular mill was wired 440VAC 3 phase with no separate 115 VAC power entry. The spindle motor can easily be switched to 220VAC. However, the 115 single phase is done internally off of the 440, and I’m unsure how to power that correctly with external source. I don’t want to fry stuff. Since this machine spent its first 12 years happily on 440VAC 3 phase, I’m thinking this is the way to go. Transformers can be had for about $100 used, plus whatever wiring necessary.

If someone has a picture inside of their Prototrak’s electrical cabinet with separate 115 single phase, that could help. Mine is a 1997 model Trak DPM with AGE3 control. Thanks all.

[Al_The_Man]

As far as the present single phase in the panel, it is most likely set up with a 440/120 or similar isolation transformer, however one side of the secondary is probably connected to panel ground for local neutral, this is easy to check, if this is how it is, it is easy to replace the control transformer with a 240/120 1 phase, or the existing one may even have the 240v taps on the primary.
It is your choice, but I would look at this avenue first.
Running the transformer 'backwards' will work, although heating may occur as often they are fitted with a compensation winding. Do not connect the star connection.
The voltage may be lower running it this way.
Al.