480 - 240 volt transformer

[CPorter]

I ran into some industrial saws that I think are not properly wired. It has a transformer wired for 480 volt primary and a 240 secondary and that is all well and good. However some of the controls on the inside use 120 volt coils and there is no connection to x2-x3 on the secondary so they have to be flowing current through ground. Center tap is not grounded and one one machine they got 75v to ground on one leg and 220v on the other and was tripping a breaker after 7 years of running ok. A similar machine next to it had 120v to ground. It doesn't make since to me at all how either are working.

 

[kwired]

View attachment 2559439I ran into some industrial saws that I think are not properly wired. It has a transformer wired for 480 volt primary and a 240 secondary and that is all well and good. However some of the controls on the inside use 120 volt coils and there is no connection to x2-x3 on the secondary so they have to be flowing current through ground. Center tap is not grounded and one one machine they got 75v to ground on one leg and 220v on the other and was tripping a breaker after 7 years of running ok. A similar machine next to it had 120v to ground. It doesn't make since to me at all how either are working.

Current can't return via ground if the source has no ground connection.

If there is no connection to x2,x3 including no grounding connection, it never worked correctly for 120 volt loads. If you were somewhat near balanced across the 240 volts with line to neutral loads it maybe worked but not with totally balanced voltages, and over time this may have caused failures if that is what is going on now. If all 120 volt control loads were on same side of the source but with no neutral connected to source - they should have never worked at all.

 

[hillbilly1]

If it worked before, and no connection to x2 and x3, most likely the saw has a control transformer built in from the factory and the 120 volt control voltage came from it. Or somebody monkey'd with the wiring seven years later, and disconnected the connection to x2 and x3. Can you post a picture of the starter?