I was out riding in the desert over the weekend with a friend/colleague of mine who set up a panel at the pumphouse on the property for a 3ph 480 open delta. Dunno what got us talking about this, but after breakfast he said that with an open delta a wiggy would not read any voltage to ground, only phase to phase. Sounded interesting so I broke out my wiggy and we opened the cover for the disconnect and found: 480v between brown & yellow, no voltage registered on the wiggy between brown/orange or orange/yellow, so he was partly correct- at least between ph1 & ph3 the wiggy registered 480, but why was the center phase registering nothing? Also checking any of the phases to ground caused the plunger to "pogo" violently off the scale. He couldn't explain what it might be and gave a vague explanation that "maybe because the panel was supplying a load or something.." At the time the panel was supplying a 480-to-120/240 transformer which was in turn powering a house on the property and his motorhome for the weekend, a pump for the well and a small florescent light in the pumphouse. Maybe the answer belongs in the theory section, but can anyone explain this one to me? Or was my friend wrong on this one? I am not very well versed in 3 phase so any information would be interesting...
