Transformer wiring 3ph step up

I recently purchased a small radial drill that has 440v only motors. I run my three phase stuff on a 240v RPC. I plan to use a 4 kva three phase step down transformer in reverse to run it. I wired it up and it seemed to run ok. When I hooked it up I used the terminals that had been used in its original application as a 480 to 240 step down. The 240 fed into X1, X2 and X3 the 480 output was from the three “2” terminals.



Each coil has six leads coming from it, three go to the primary terminals and are marked 1, 2 and 3. one goes to the secondary terminals and is marked X1 or X2 or X3. One lead from each coil is soldered together and the last three (one from each coil) go to the two terminals marked HOXO. One lead goes to the first HOXO and the two others are paired together at the last HOXO. The two HOXO terminals are not connected together.



Shouldn't the three leads going to the HOXO terminals be ties together? Could someone please explain how this is wired internally and is it set up right for my purpose?

You are good to go with x1,x2,x3 for the 240 side & 2,2,2 for the 480 side.

LEAVE THE HO & XO ALONE UNLESS YOUR MACHINE INSTRUCS YOU TO DO OTHERWISE. AND DO NOT TIE THEM TOGETHER.

Which it does not in this case Your 440 motor does not care if the nuetral of the wye (Y), or Ho in this case, is grounded or not. So leave H0 alone and unhooked.

Your RPC will very much care if you ground this transformer's neutral (X0) - it probably will blow some stuff up VERY quickly as it is an RPC and not a wye source itself - the xfmr Y is at a completely different voltage than your RPC ground - hook it up and watch sparks fly, breakers pop, and smoke come out of lots of things faster than you can turn it off.

You have a Y connected transformer. The center terminals are available if someone wants to pick off the voltage from each coil, but there is no need to here. If you do a continuity check, you should find that the HOXO terminals are not connected. You may want to ground the one for the 480V windings, but grounding the 240V one could cause trouble. For example, in this area the B phase is grounded. Grounding the center of the 240V Y would put a short right across the line.

Bill

heehee... 9100, he said he is running off RPC not 3ph 208 grounded corner delta......

Since he is running on RPC, he has 240v 1ph coming in. His GROUND is at 120v with respect to each 240v leg from his house that he is putting into his RPC.... each winding on the xfmr has 240/square root 3 or 208v across it; hence his X0 wye on the 240v transformer is at 208v from each house leg. this is not 120. hence, it would be like tying 208v across his 120v loads and could blow lots of stuff up - not just at the RPC and anything connected to it, but possibly all thru the house.

If not married, that's prob ok, and a few beers would make it funny after a while, but if married he may be kicked out to live in the workshop with his beloved smoked RPC (RIP) for company for quite some time....

Thanks for the info. I guess I'll go with "if it ain't broke, don't fix it" and leave it wired like it is.