I recently came across a YouTube video where a guy rewound a microwave transformer to make a spot welder.
In talking about it, he stated -- and repeated -- that it was very important for the secondary winding to have the same "sense" as the primary -- that is, both windings had to go around the core in the same direction.
I know that matters if the transformer is handling very asymmetric waveforms such as in a flyback configuration, but I have never heard that it matters for plain old 60 Hz. sinusoids.
Does it? Or was the guy just confused?
Isaac