Strange Voltages

[jOmega]

Gentlemen:

Phase-to-Phase voltage is 240-240-240

Phase-to-ground is 120 120 208

Theories, Ideas, Explanations, greatly appreciated.

jOmega

 

[lakevillethor]

Open delta configuration. It's a vector diagram. 208 = 120 * (sqrt of 3).
-AT

 

[stevenal]

Whether open or closed, these are the voltages you see on a 120/240 delta. One winding is center tapped and grounded giving 120 V on the adjacent phases to ground, and 208 on the wild leg.

 

[Jerry123]

This may help.

http://aetech.com/images/pdf/02cadmsample.pdf

 

[dpc]

As stevenal says, this appears to be a wild-leg delta system, where one of the secondary windings is center-tapped and grounded.

 

[jbartos]

Suggestion: Follow your conductors from your building (if this is the case) until you see a pole with two overhead transformers. They are connected in open delta connection on their secondary side. One transformer is center tapped to obtain neutral and 120V to each winding end of the transformer. The transformer end to the other end of transformer will have 240V. The center tapped transformer connection with respect to the other transformer far end not connected to the center tapped transformer will exhibit 208V with respect the center tapped point called neutral.

 

[jbartos]

Suggestion: Visit

http://www.tpub.com/content/construction/14027/css/14027_75.htm

http://www.patchn.com/deltasys.htm

http://home.att.net/~benmiller/elecsys.htm

etc. for more info