I would think that as far as toob transformers are concerned, the voltages between the windings would be too great to wind them bifilar.
Transformer question
Sep 25, 2004
27 Replies
Using the proper insulation on the magnet wire and, if necessary,
vacuum-impregnating the transformers pretty much takes care of that
problem.
You're right.
snip
Try shorting out one of the windings while measuring across both. If you get the single coil reading it's the inductance and DMM sampling that's doing this.
Now I'm the one who's confused, because any way we do this, there are still 2 separate windings, unless you want to count the one on top of the other as a single center-tapped winding.
Yes, note that 225.58 + 539.72 = 2 x 382.65. This was what I predicted.
Yes, but the only way you can get this is to suddenly have more room to do windings, so it's not really a fair comparison.
You'd have to assume that the voltage difference between adjacent ends of the bifilar winding would be nearly as great as the B+ voltage. I'm not sure how much I can expect to get out of magnet wire varnish, but I'm pretty sure that I wouldn't want to count on this if I were making a bunch of them to go out into the commercial world running on a 400V B+ line.
Keep in mind also that this voltage difference would be AC, reversing itself with the output. This is a lot harder on the insulation and is a sure way to find flaws in the insulation. The ACVrms between wires at either end would be about .7 x B+. The voltage difference in the middle would actually be the same. Interesting how that works out....
Sure I could probably make one and show that it worked just fine, but what would my return rate be when they went out into the field and people covered the ventilation slots with magazines and dirty clothes, while playing the stereo at full volume for hours on end. ;-)
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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Separate windings as on two separate bobbins, each with the same width
and starting diameter and occupying a separate portion of the core.
Sure, you can do that, but you're changing the rules in the middle of the game: You're giving yourself a larger winding window to work with. (otherwise you would have slightly less than half as much length to work with, so each winding would build up faster and taller. The extra bobbin takes up some of your previous volume, so you come out behind.
Otherwise, separate bobbins is certainly a desirable thing to do, but you have to allow extra space for it up front.
I could also suggest that I would just start with a longer core so that I would need fewer layers, and that would save even more wire....
That's a MUCH easier problem than 300-500 AC volts between adjacent turns.
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
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At the expense of extra core or, for the same volume, a longer
magnetic path (not good). The game is to minimize the total cost of
the transformer while maximizing its performance, and blithely doing
this-and-that isn't likely to converge on a winning "design"
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