can you use it? 208 of a 240 delta xfmr

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alexveres@yahoo.com

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as far as i asked around nobody knows the answer, and nobody did it before:
i have an high leg delta system with 240/120 and 208 on the"high leg" to the neutral.
i need 208, can i use the 208 from the high leg, or not? are there any problems deriving from this?


The line to line voltages are all the same:

Vab = Vbc = Vac = 240V
Because the winding between the 'A' and 'C' phases is center-tapped, the line-to-neutral voltages for these phases are as follows:

Van = Vcn = 120V
But the phase-neutral voltage for the 'B' phase is different:


Vbn=120 X sq root of 3 = 208
 
V

Volta

Senior Member
Location
Columbus, Ohio
Makes for a lively debate . . .
It is allowed by the NEC.
As Buck said, there are some fluctuations to the voltage, or so we hear.
I think it is fine with simple resistive loads, like a heater.
You need a straight rating breaker (240), rather than slash (120/240), too. Hard to find in single pole, but you can use one pole of a 2 or 3-pole unit.
 
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alexveres@yahoo.com

Member
equipment

equipment

i need the 208 for equipment that has electronics, and motors in it 4X25A.

as i said in the first post it appears that nobody realy did it, and it is only speculations, the only thing i found about this is the following:

" Since one phase-to-neutral voltage (phase 'B') is higher than the others, no single phase loads can be connected to this phase. This eliminates the ability to use one third of the breakers in a panel for single-phase loads. Further, the lack of loading on the high leg will result in an unbalanced load. However, many new fluorescent ceiling fixtures utilize ballasts which automatically sense line voltage. These fixtures are designed to operate on voltages from 110 to 277 volts. Use of modern fixtures in conjunction with code compliant wiring may allow selected lighting to be placed on the high leg, thereby eliminating this drawback."

it appears that is ok to connect a lighting load to it...

basicaly i will be using from the transformer one winding from one phase , and half winding from another phase in series, and because of the phase shift, the way the magnetic field flows thru the armature, or something i don't fully understand, it is 208 instead of 240+120, therefore i'm wondering if this resulting 208 will deliver the same rated ampacity as the regular phases at 240.
 
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