2 phase bridgeport on 3 phase power

[unitedmachineworks]

hi we recently joined this forum. We have a question we hope you could help us with:
We recently purchased a bridgeport milling machine that runs on 240/2 phase. we have 240/3 phase. could we run it on the 3 phase or do we need a transformer of some sort???

thanks in advance for taking the time out to answer our question.
Edward & Heather ZOll

http://www.UnitedMachineWorks.com

 

[busbar]

A suggested 'minimal' transfomer configuration using a {smaller} buck/boost 120x240—16/32V transformer follows, in an abridged description that does not discuss required overcurrent protection and motor control/switching. It may be possible to power the motor(s) conditional on the 2ø motor(s) being 4-wire 240V with 2 isolated coils, and the 3ø-delta service 240/120V 4-wire. [Motor nameplate data would be handy.]

With conductors A-B-C-N of the 3ø-delta source, Aø and Cø would connect to one coil. Bø would connect to one lead of the other coil, along with transfomer H1. “Dø” would be derived from leads H4-X4 of the buck/boost transfomer, with H2-H3 tied and taped off, X1 is connected to 3ø N terminal, X2-X3 tied and taped off, with “Dø” connected to the remaining lead of the second coil on the 2ø motor(s). So, one isolated coil is powered by A and Cø. and the other by B and the derived “Dø”. This configuration is intended only for the case where the midpoints of the two stator windings are not connected.

 

[unitedmachineworks]

this machine is actually a cincinatti verticle mill and it is a true 2 phase motor 5 conductors dc .it has a spindle motor 2 hp and a power feed motor which is also 2 phase and was made around 1960. it does come out of the philadelphia area. in laymans terms is their any way to run this.thanks

 

[jbartos]

Suggestion: Three/two-phase connections:
1. Scott Connection. This requires two transformers (main and teaser) with different tappings and ratings (they may be constructed for interchangebility).
2. Le Blanc Connection. The 3-phase side consists of three winding in star or delta, wound on an ordinary 3-limbed core. The secondary windings have to be properly grouped to form to power 2phase balanced load. The connection has the advantage of using a standard 3-phase core.

Reference:
M. G. Say "Altarnating Current Machines," John Wiley & Sons, 1978, page 169

 

[busbar]

UMW — Can you verify that the local electrical service is indeed 3ø 240/120V 4-wire delta? Will you post the nameplate data from the 2ø 5-wire {AC} spindle and feed motors?

A 208–120/240V 1ø transfomer may do the job—but it might be a master-electrician project. {One discussion is Ch. 10 §8-9 in Pender & Del Mar, Electrical Engineers Handbook, Wiley and Sons, 1949.}

 

[Skogsgurra]

"was made about 1960"

Two-phase in those days? No way!

I think that cbarn may be right when he says DC. That is also what unitedmachineworks says en passant. It would explain the five wires. Two for the field winding, two for the armature and one for PE.

It has been an interesting discussion. And I am not quite sure that it is over yet...

 

[jbartos]

Suggestion: If transformers are not convenient or hard to find, perhaps, an ac-dc-ac converter may be used. It would probably have to have a custom-made output. Why not to say "Viva Power Electronics!"?

 

[busbar]

unitedmachineworks — Any news on powering your mill?