23-10-2023, 08:34 AM
Side-by-side windings, as in split-bobbin mains transformers, doesn't give as good coupling as one on top of the other. It may not matter in a mains transformer very much, but it can curtail the higher audio frequencies due to the greater leakage inductance.
Primary or secondary first? At an elementary level, it doesn't matter - minimum total loss occurs when primary and secondary losses are equal anyway, and that's easy to contrive by appropriate choice of wire gauges.
From a practical point of view, winding the fine wire first is slightly easier, because it goes around the square corners of the bobbin with less strain and less bulging. When it comes to wind the secondary, the corners are already rounded off by the primary, so the winding is easier.
Myself, when I wind an output transformer, I generally section the windings (even in basic single ended transformers), and I do put half the secondary first, then the full primary, and then the remaining half secondary. I use multistrand wire for the secondary so it's more flexible to go round the more abrupt inner corners, and after finishing the first half-secondary I coil up sufficient length to finish the job and tape it to the side of the winding mandrel while I'm winding the primary, so I can bring it back in for the other half-primary afterwards, with no internal joint. That would hardly be practical with oodles of metres of primary, if I did it the other way round.
Primary or secondary first? At an elementary level, it doesn't matter - minimum total loss occurs when primary and secondary losses are equal anyway, and that's easy to contrive by appropriate choice of wire gauges.
From a practical point of view, winding the fine wire first is slightly easier, because it goes around the square corners of the bobbin with less strain and less bulging. When it comes to wind the secondary, the corners are already rounded off by the primary, so the winding is easier.
Myself, when I wind an output transformer, I generally section the windings (even in basic single ended transformers), and I do put half the secondary first, then the full primary, and then the remaining half secondary. I use multistrand wire for the secondary so it's more flexible to go round the more abrupt inner corners, and after finishing the first half-secondary I coil up sufficient length to finish the job and tape it to the side of the winding mandrel while I'm winding the primary, so I can bring it back in for the other half-primary afterwards, with no internal joint. That would hardly be practical with oodles of metres of primary, if I did it the other way round.
