1. If the number of turns is relatively small, such as the 400V low voltage of distribution transformer, only 10 turns, you can use foil, that is, aluminum foil or copper foil (tape).

2. If the number of turns is large, multiple wires are wound in parallel, and the number of wires is small, so the winding is relatively simple and the transposition times are few. On the contrary, the winding is more complicated and has more transposition times. In addition, the large number of joint elements will also bring the benefit of reducing extra loss.

Because there are many kinds of transformers, I don't know what kind of transformer you are, how thick the wires are, and so on. The above two items are power transformers. Therefore, if the above suggestions are not suitable for you, or are too general, then you should make some supplements.