It is wild because it is higher than 120V.
Well I grew up in the suburbs, but if I walked out my back yard, crossed a small farm field, crossed a shallow creek, another small field, and waded across another bigger creek, I could be in Philly in maybe 10 minutes. So I worked around 2 phase all my life. Last one was a generator repair, maintenance and testing at the Youth Study Center. I think it was about 500 KW 3P and had a Scott T in between the gen and the transfer switch. It's been too long ago for me to remember the specifics of the equipment. What I remember was looking at that big 2 Phase transfer switch and wondering wth that cost.
Just found this online
I don't ever see voltage fluctuations in Delta 240 single phase 2-pole circuits using 1 leg of wild. Only line to neutral on the wild leg.
It's called a wild leg by some and a high leg by others. In both cases it's because the voltage to ground is higher than 120V.
I've seen variations on open delta 3 phase loads. Spent a lot of time rolling phases on motors to get things balanced out, none of them had any connection to the high leg.
The less loaded the motor was the longer it may last. Amount of usage it sees also factors in. Something running occasionally can take more voltage and current imbalance abuse than many think compared to same abuse if it ran rather continuously.
I agree with you, when utility supplied it usually is pretty stable voltage, there is more impedance in that path like you mentioned also. Full vs open delta does factor in as well. Full delta has parallel path from high leg to neutral through the delta where open delta only has one path. Imbalancing load on full delta should likely cause one path to have less impedance than the other during that condition, but current will still take both paths in proportion to those impedances.
I never seen one vary by that much. I do agree loading conditions will make it vary but most around here will run about 248 to 250 unloaded line to line with high leg at about 214 or 215. Any drop when loaded typically has similar percentage drop line to neutral including high leg to neutral as line to line drop, especially with full delta systems. I could see some more extremes if you have a large lighting pot and a small stinger pot for an open delta and you basically load the high leg to more than the rating of the stinger pot, but also don't think you would see as low as 135 volts unless they have such high overcurrent protection on their transformer that it won't open until the primary winding has actually faulted out.
I don't think so. The lack of proper rated breakers, limited availability and/or price if they are attainable usually is what discourages it.
We rolled a lot of motors with hi leg open deltas. Usually could get a more balanced load.
?? If there are three phases how can you discount the wild leg phase?
The high leg doesn't play any role in three phase loads, or line to line single phase loads. Any fluctuation in the voltage from high leg to neutral is accounted somewhere else in the system. It has to be.
Really any voltage instability would be due to it being an open bank, and not having that third trans. If you think about it. a tap in the middle of a secondary connected to the MGN and the customer's service drop neutral, really doesn't mean much
