On Wednesday, August 8, 2018 at 2:24:52 PM UTC-4, Bob wrote:
On 8/8/2018 1:43 PM, trader_4 wrote:
I've described it quite clearly before. Take your scope, hook the
scope ground to the neutral, which after all is the SYSTEM reference
point, by design, not some random, bizarre point I picked. Put
one probe on one hot, put one probe on the other hot. You'll see
two 120V sine waves, 180 deg out of phase with each other.

The transformer secondary winding has two ends, L1 and L2.Â* Put your scope common lead on L1.Â* Attach one trace probe to the secondary tap and the other trace probe to L2.

Your scope should display two traces in perfect sync that vary only in amplitude.Â* Pure single phase.

You can't ignore the central tapped neutral as if it was some insignificant
detail. It's the whole, essential point of the circuit. By center tapping
it and defining that center point as the system NEUTRAL and reference point,
you have created TWO 120V voltage sources. The parlor trick is to only put
the scope across the two hots and ignore the very important phase relationship
between each hot and the neutral/reference point.

Draw us the model circuit that shows what's going on there without using
TWO 120V voltage sources that are either 180 deg out of phase or
of opposite polarity, which is the same thing. It can't be done.