kiki_danc said:
Btw.. in the 3 phase open delta.. one of the wires when tested against ground is 210 volts.. while the other 2 of the 3 phase is 120 volts.. Open Delta really do this? When the 210volts line is tested against one of the 2 other.. it is back to 120 volts.. what kind of phase manipulation can do this?
Look up 'high leg delta"
equilateral triangle 240 volts per side
by geometry distance from from L3 to N(more precisely to center of base) is √(240
2 -120
2) = 207
and that's what you ought to read.
That you measure just 210 suggests to me that there's not anything really unexpected there.
Open delta just omits one of the transformers
(and that used to be a common delivery scheme in US but they're discouraging it in Colorado and some other states.)
so the triangle can distort if the transformers are electrically less than 'rigid'
kiki_danc said:
When the 210volts line is tested against one of the 2 other.. it is back to 120 volts.. what kind of phase manipulation can do this?
Get an architect's scale and drawing compass
construct yourself a triangle to scale with sides in proportion to your measured voltages
base L1-L2 = 240 (or whatever you measure) units long
""210 volts line is tested against one of the 2 other.. it is back to 120 volts.""
tells me L1-L3 and L2-:L3 are both 120
and L3-Gnd is 210Can you draw a triangle that meets those constraints?
Kirchoff's voltage law says the voltages MUST form a closed geometric shape , and with just three terminals it has to be a triangle but not necessarily equilateral.
Voltage between ground and Neutral terminal in middle of bottom transformer is unknown .
You should be able to find it from voltage measurements and graphics.
Make careful measurements and double check them for it's tedious redrawing the triangles
You might find there's voltage between N and Ground . Especially if there's no wire on N..
Or you might find the triangle isn't quite equilateral and L3 isn't right above N.
Anyhow that's an exercise you should undertake to deepen your understanding.
Keep up the good work and you'll become the " Go To Guy " fpr electrical
but keep in mind - "The biggest part of being smart is being aware of how little we know."
Mother Nature reminds me of that frequently.
old jim