On Wed, 11 Sep 2019 20:08:14 -0500, Dean Hoffman
wrote:

On 9/11/19 7:32 PM, trader_4 wrote:

Cut a bunch.

And again, if you would follow the very simple example I gave using
Ralph's 90 deg two phase, you'd see how electrically it is the same
as 240/120 with the exception that the phase angle is 180, instead of
90. Again:

Ralph's two phase is two phase, yes? It was three wires, 0 deg
phase hot, 90 deg phase hot, common neutral return, yes? OK,
make it 100 deg phase difference, which of course we could easily
do. Would there still be two phases
there? Make it 179, still two phases? Make it 180, what do you have
now? Still two phases or did something mysterious just happen?
And don't say those phases are "weird", it's irrelevant. We can
write the equations, solve them, for any phase angles we want.
Of course the answer is that there are still two phases there.
And then what you have is electrically the same as the 240/120 service.
They are indistinguishable. That's the beauty when you approach
things like an engineer, logically. If you don't treat it that way,
then you have holes where what should be elegant, logical and
continuous, falls apart.

Question. Would the two phase motors from days of yesteryear
start without capacitors?

Yes, just like a 3 phase motor since you already have a phase shift.
That is another indication that single phase is just that, you still
need a capacitor to create a phase angle no matter how you connect a
single phase motor. They do make shaded poll motors that start
without a capacitor but they do a trick with the shaded pole winding
that makes it look like there is a phase shift. They don't have much
starting torque tho.