unbalanced three-phase system

[raph.yyz]

Hi guys,
I am new to this forum and also new to the engineering world.
We have a machine down in south America connected to a source panel that has no ground wire. The only ground is from our machine to a stake in the ground. We were therefore not able to check the voltages from phase to ground at the switch in the source panel. The voltages from phase to phase at the source panel were between 213 and 216V. The phase to phase at our machine was 230 to 234 V. We then checked the phase to ground at our machine electrical cabinet. The voltages were 284, 296 and 455V. I?m guessing the 455V is the ?wild leg?. I believe the machine is connected to an unbalanced three-phase circuit resulting from an ungrounded open delta transformer that we cannot remove because the main source is apparently miles away.

I need to have 240V leg to leg and therefore 120-140V leg to ground (I am still not sure if the voltage between leg to ground is that important for us...).
How is that possible? can I simply add a 2:1 delta/Wye transformer after their open delta transformer?

Thanks for your help guys,
Raph

 

[petersonra]

Re: unbalanced three-phase system

I don't see how the voltage can increase going from the source to your machine unless there is some kind of transformer in the middle.

You don't need a grounded conductor if you have a delta configuration.

It is not unusual in an ungrounded delta for the voltage to ground to be slightly different from different phases as there is no direct ground reference.