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Re: [TCML] bipolar coil



Hi Kris,

Using the 9/60 NST, SRSG LTR is .046uF. Doubling this for the bipolar situation is just too much cap (resulting in less than 1 turn). Remember, you don't have to go this big with the cap. Say you use the 1.6 x Cres value which is .0265uF. Thus doubling this you would input .053uF for the cap size. When you tune, you'll end with 2.2 turns per coil. Thus each coil will have 1.245uH for a total of 2.49uH with the .0265uF cap. Each coil will be resonant at 410kHz (assuming each twin is 2.375" x 11.5", 975 turns, 30 awg, with 3"x12" toroid).

I'm not trying to suggest that 0.0265uF is the value to use, but simply to show that a smaller cap size is needed so that you can transfer more turns to each primary coil. The above assumes 1.6uH of lead inductance (I used the full 48" lead inductance considering the model needs to see all of it). If you can reduce the wiring to bare minimum, you can then transfer that inductance into the primary turns as well. Right now, it is being shared with the primary and it is a significant at 36% of the total inductance.

For clarification: Your original post identifies twin coils, not a bipolar coil. Is this correct? You were using the program in a bipolar configuration simply to try to model the situation? That's how I interpreted.

The reason I ask, is if this were actually a bipolar coil, I would model it very differently.

Take care,
Bart

Kris Grillo wrote:
I have wound the coils and put about 25 coats of poly on them, and made the toploads. In fact, everything is done except for the primaries.
I do realize that 1350VA is a huge amount of power for such a small coil. I think I got a little carried away. Originally I was going to use just one of the 60mA transformers, but then I found another one real cheap, so I bought it. I had another 30mA sitting on the shelf and figured what the hell, lets make a monster of a small coil. I think I'll just stick with the original plan of 60mA.

Bart, I tried inputing just one of the twins and doubling the cap size. I get a geometry error, less than one turn primary. I also tried it with 120mA, 90mA, 60mA and 30mA, all with the same results. This was with 2x the recommended LTR cap size for a synchronous rotary gap for each of the currents. I tried it with double 2x resonant also, with the same results. I haven't tried tweaking the primary dimensions, except for spacing the coupling. Any suggestions?
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