single to 3phase conversion

[Yorkie]

On a similar tack (transformer lams), many years ago when radio amateurs often actually built things, I recall that we used to use microwave oven transformers in which the secondary had burnt out and strip off all the old wiring and wind on 1.5mm (house wiring wire) to create a low voltage transformer for 13.5V power supplies. As I recall, it was about 1 turn per Volt, so only needed about 15 or so turns to get 15V. What I couldn't understand at the time, and still don't, is that the lams had weld runs across them to weld them together. I guess in part to stop them vibrating, but with my slim to non-existent knowledge of transformers, I couldn't understand why that didn't create a shorted turn. Obviously it doesn't, but I know for example, of people who have inadvertently created a shorted turn on a toroid transformer by allowing the top of the securing bolt to come into contact with the metal chassis to which the other end of the bolt is screw, with predictable consequences.

All of this only serves to remind me to steer clear of single/3-Phase conversion and to realise what an impressive job Colin ('retired') did of his set-up, which I've seen in operation!