
>Although 208 volts might not work on some 240 volt machines, hopefully
>just a few volts away would achieve that. Boosting each 120 volt leg
>to 136 volts with a 120>16 volt transformer would give you 235.5589
>volts linetoline. That might be enough. But if one really needs to
>get closer, there are other configurations.

 Phil, why do you use terms like 235.5589 volts? No electrical
 engineers do that. It is improper usage and unprofessional to imply
 precision to 4 decimal places for common electrical circuits.
The precision
_IS_ there ... because the number is the result of an
arithmetic calculation using a high level of precision with a formula
I believe to be accurate. This is very different than if I were to
physically measure the voltage of a circuit with a voltmeter that has
4 digits of accuracy and precision. In the latter case you would see
me write "235.6" or whatever it happens to be.
It is an accuracy vs. precision issue. Accuracy is needed in order to
correctly reflect the mathematical formula used. In the event some other
formula results in a value somewhere near there, that would when rounded
in the practical manner yield the very same result, the accuracy value
is what will distinguish the different formulas. Precision is then how
the value is expressed to carry the accuracy (of the calculation).
Although in this case I do not know of another formula that could give
a result close enough to, when rounded, appear to be the same, I cannot
rule out some formula existing. In the past I have run into cases where
entirely different formulas ... formulas that are not mathematically the
same (e.g. one cannot be transformed into the other), give results that
are closer to each other than the practical precision normally used.
So ... as a standard practice, when numbers are produced as a result of
doing mathematical/arithmetic calculations, I use enough precision to
give a very high level of confidence in matching the correct formula.
Sometimes I express a precision as extreme as arithmetic being performed
can do. Sometimes I reduce it some for convenience, but leave enough to
be sure there is likely no ambiguity as to which formula is used.
Someone wishing to review my calculations can then match the numbers very
closely to be sure that not only am I using the correct formula, but am
also using valid trigonmetry implementations (e.g. code I did not write).
If I measure a voltage with a voltmeter, I will express it as precisely
as the device is capable of accurately measuring and precisely displaying.
If it has an accuracy of 1/10 of a volt in a 200 volt range (rather good)
I'll use that and might state the voltage as "119.1" or "121.0". But if
it only has an accuracy of 1 volt, I'll state it as "119" or "121".
So when you see me use a highly precise expression like "235.5589", it is
coming from a mathematical calculation done with at least 6 or 7 digits
of precision (probably more since I default to using the double type which
has 14 or so digots), using a formula I believe to be accurate.
If I ever manage to make a real physical measurement with such accuracy,
I'll be sure to let you know about that miracle device capable of doing
such a thing.
 You have some unique and original ideas, but it almost seems that you
 are off in a different electrical world somewhere, with your own
 standards and conventions.
Like doing mathematical formula based programming to automatically explore
lots of models?
Here is the output of one of my programs that explores a variety of ways
to configure different buckboost transformers, including 480/240/120 volt
transformers, and running transformers at much lower than design voltage
just as a means to get a desired ratio (e.g. 208 volts being fed to a
transformer designed step 480 volts down to 120 just because that is the
only common transformer to get a 4:1 ratio).
The first 2 mumeric colums give the resultant system (at calculation level
precision slightly reduced to fit the output format). The 4th and 5th give
the voltage being added to 120 volts, and the phase angle of that added
voltage vector. The 6th gives the buckboost transformer primary voltage,
and the 7th and 8th describe the buckboost transformer being used.
Notice the two "103.923048" volt results. They are really the same thing
in a geometric/vector sense, even if the configuration to arrive at them
are different. The precision of the expression reveals that.
Notice the rows with "228.630707" and "228.945408". Those are
_different_
kinds of configurations that are
_not_ the same as vector math goes. The
fact that the numbers are different reveals this. If these had been
rounded, that fact would be hidden. If you measured them with a typical
voltmeter, you wouldn't know as both might read "229".
There are other examples of close numbers in this list.
103.923048 Y
/ 60.000000 : 120.000 + 60.000 @ 180 (120.000 via 240 > 120)
103.923048 Y / 60.000000 : 120.000 + 103.923 @ 150 (207.846 via 240 > 120)
137.477271 Y
/ 79.372539 : 120.000 + 51.962 @ 150 (207.846 via 480 > 120)
152.420471 Y / 88.000000 : 120.000 + 32.000 @ 180 (120.000 via 120 > 32)
166.276878 Y
/ 96.000000 : 120.000 + 24.000 @ 180 (120.000 via 120 > 24)
168.000000 Y / 96.994845 : 120.000 + 27.713 @ 150 (207.846 via 240 > 32)
177.583783 Y
/ 102.528045 : 120.000 + 20.785 @ 150 (207.846 via 240 > 24)
180.000000 Y / 103.923048 : 120.000 + 60.000 @ 120 (120.000 via 240 > 120)
180.133284 Y
/ 104.000000 : 120.000 + 16.000 @ 180 (120.000 via 120 > 16)
181.865335 Y / 105.000000 : 120.000 + 15.000 @ 180 (120.000 via 120 > 15)
183.597386 Y
/ 106.000000 : 120.000 + 14.000 @ 180 (120.000 via 120 > 14)
185.329436 Y / 107.000000 : 120.000 + 13.000 @ 180 (120.000 via 120 > 13)
186.418883 Y
/ 107.628992 : 120.000 + 32.000 @ 120 (120.000 via 120 > 32)
187.061487 Y / 108.000000 : 120.000 + 12.000 @ 180 (120.000 via 120 > 12)
187.445992 Y
/ 108.221994 : 120.000 + 13.856 @ 150 (207.846 via 240 > 16)
190.494094 Y / 109.981817 : 120.000 + 24.000 @ 120 (120.000 via 120 > 24)
192.468179 Y
/ 111.121555 : 120.000 + 10.392 @ 150 (207.846 via 240 > 12)
193.989690 Y / 112.000000 : 120.000 + 8.000 @ 180 (120.000 via 240 > 16)
195.468668 Y
/ 112.853888 : 120.000 + 16.000 @ 120 (120.000 via 120 > 16)
196.150452 Y / 113.247517 : 120.000 + 15.000 @ 120 (120.000 via 120 > 15)
196.845117 Y
/ 113.648581 : 120.000 + 14.000 @ 120 (120.000 via 120 > 14)
197.453792 Y / 114.000000 : 120.000 + 6.000 @ 180 (120.000 via 240 > 12)
197.552525 Y
/ 114.057003 : 120.000 + 13.000 @ 120 (120.000 via 120 > 13)
198.272540 Y / 114.472704 : 120.000 + 12.000 @ 120 (120.000 via 120 > 12)
201.275930 Y
/ 116.206712 : 120.000 + 8.000 @ 120 (120.000 via 240 > 16)
202.849698 Y / 117.115328 : 120.000 + 6.000 @ 120 (120.000 via 240 > 12)
208.624064 Y
/ 120.449159 : 120.000 + 10.392 @ 90 (207.846 via 240 > 12)
209.227149 Y / 120.797351 : 120.000 + 13.856 @ 90 (207.846 via 240 > 16)
210.940750 Y
/ 121.786699 : 120.000 + 20.785 @ 90 (207.846 via 240 > 24)
213.232268 Y / 123.109707 : 120.000 + 6.000 @ 60 (120.000 via 240 > 12)
213.316666 Y
/ 123.158435 : 120.000 + 27.713 @ 90 (207.846 via 240 > 32)
215.109275 Y / 124.193398 : 120.000 + 8.000 @ 60 (120.000 via 240 > 16)
218.238402 Y
/ 126.000000 : 120.000 + 6.000 @ 0 (120.000 via 240 > 12)
218.979451 Y / 126.427845 : 120.000 + 12.000 @ 60 (120.000 via 120 > 12)
219.970453 Y
/ 127.000000 : 120.000 + 13.000 @ 60 (120.000 via 120 > 13)
220.970586 Y / 127.577427 : 120.000 + 14.000 @ 60 (120.000 via 120 > 14)
221.702503 Y
/ 128.000000 : 120.000 + 8.000 @ 0 (120.000 via 240 > 16)
221.979729 Y / 128.160056 : 120.000 + 15.000 @ 60 (120.000 via 120 > 15)
222.997758 Y
/ 128.747816 : 120.000 + 16.000 @ 60 (120.000 via 120 > 16)
223.615742 Y / 129.104609 : 120.000 + 10.392 @ 30 (207.846 via 240 > 12)
226.495033 Y
/ 130.766968 : 120.000 + 51.962 @ 90 (207.846 via 480 > 120)
228.630707 Y / 132.000000 : 120.000 + 12.000 @ 0 (120.000 via 120 > 12)
228.945408 Y
/ 132.181693 : 120.000 + 13.856 @ 30 (207.846 via 240 > 16)
230.362757 Y / 133.000000 : 120.000 + 13.000 @ 0 (120.000 via 120 > 13)
231.447618 Y
/ 133.626345 : 120.000 + 24.000 @ 60 (120.000 via 120 > 24)
232.094808 Y / 134.000000 : 120.000 + 14.000 @ 0 (120.000 via 120 > 14)
233.826859 Y
/ 135.000000 : 120.000 + 15.000 @ 0 (120.000 via 120 > 15)
235.558910 Y / 136.000000 : 120.000 + 16.000 @ 0 (120.000 via 120 > 16)
239.699812 Y
/ 138.390751 : 120.000 + 20.785 @ 30 (207.846 via 240 > 24)
240.399667 Y / 138.794813 : 120.000 + 32.000 @ 60 (120.000 via 120 > 32)
249.415316 Y
/ 144.000000 : 120.000 + 24.000 @ 0 (120.000 via 120 > 24)
250.567356 Y / 144.665131 : 120.000 + 27.713 @ 30 (207.846 via 240 > 32)
263.271723 Y
/ 152.000000 : 120.000 + 32.000 @ 0 (120.000 via 120 > 32)
274.954542 Y / 158.745079 : 120.000 + 60.000 @ 60 (120.000 via 240 > 120)
274.954542 Y
/ 158.745079 : 120.000 + 103.923 @ 90 (207.846 via 240 > 120)
289.309523 Y / 167.032931 : 120.000 + 51.962 @ 30 (207.846 via 480 > 120)
311.769145 Y
/ 180.000000 : 120.000 + 60.000 @ 0 (120.000 via 240 > 120)
374.699880 Y / 216.333077 : 120.000 + 103.923 @ 30 (207.846 via 240 > 120)

/
 Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below 
Click to see the full signature.