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bi polar primary wiring

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Kristian

Sat Apr 12 2008, 12:34PM

Registered Member #611 Joined: Wed Mar 28 2007, 11:40PM
Location: Hudsonville, Michigan
Posts: 79

I have wound two identical 2" secondaries to use in a bipolar configuration on a small nst powered coil. I have the nst wired in parallel to the terry filter and the safety gap. The synchronous rotary gap is in parallel with the safety gap. The MMC is wired in series with the primaries and those are in parallel with the srg. I'm assuming that the two primaries should be parallel with each other with the inside turns connected to the MMC and the outside turn taps connected to the spark gap, like mirror image primaries. Does this sound right? Does anyone have a schematic for this configuration that they could post to clarify this wiring for me?

Coronafix

Sat Apr 12 2008, 01:48PM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

You can consider the two primaries to be just one that is split in the middle, just like
considering the two secondaries as one long 1/2 wave coil rather than two 1/4 waves
connected in the middle. Does that help?

northern_lightning

Sat Apr 12 2008, 04:31PM

Registered Member #1348 Joined: Sun Feb 24 2008, 01:48AM
Location: Michigan's Upper Peninsula
Posts: 22

say, for example, you have a bipolar setup with two identical secondaries, each 2 inches in diameter by 8 inches tall.

when calculating their combined bipolar resonant frequency do you
a) treat the two secondaries as one large secondary with a diam. of 2" and a height of 16" and calculate the resonance based on the inductance and self capacitance for a coil of these dimensions. or
b) view the two coils as separate, calculate the inductance and self capacitance of each 2" x 8" coil (values should be just about identical), add the results for the two, and then derive the resonant frequency from these numbers?

(a) and (b) would give two completely different resonance values. and (b) cannot be derived from simply splitting the values of (a) in half. basically what i'm wondering is: should the two secondary coils be viewed as two isolated inductances in series since they are separated by distance? if not, why? i'm confused. (insert perplexed emoticon here)

Kristian

Sat Apr 12 2008, 06:17PM

Registered Member #611 Joined: Wed Mar 28 2007, 11:40PM
Location: Hudsonville, Michigan
Posts: 79

Primaries diagram

This is what I was thinking for the primaries. The round thing that looks like a button is the rotary spark gap (I forgot to label it). I was thinking that I would tune each primary and secondary as individual coils.

northern lightning, my math gets a little fuzzy here. I think option b would be correct for this configuration. I'm not sure how to calculate the frequency of the primaries with the capacitor bank. I'm thinking I would just calculate the frequency for one primary / secondary and match that on the second set. I may be way off on this. I got to this point and shelved the project for weeks while I thought about it for a while. I figured I would ask if anyone here could point me in the right direction for wrapping my brain around this.

Arcstarter

Sat Apr 12 2008, 07:23PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Well a bipolar tesla coil has only one primary. Check this out:

It has just one primary,as should be. The purpose of a bi-polar tesla coil,i figure,is to have two outputs on the secondary so you have the same output voltage but it have basically a 'hot' and a 'ground' even though neither of them are either one of them, Just make a regular tesla coil and move the primary to the middle. I could be wrong about all this but i think i am spot on.

Kristian

Sat Apr 12 2008, 08:05PM

Registered Member #611 Joined: Wed Mar 28 2007, 11:40PM
Location: Hudsonville, Michigan
Posts: 79

More like this
or a much smaller version of the Gemini coils

Has Capper been around here lately? I know he has made a couple of coils like what I'm talking about.

Arcstarter

Sat Apr 12 2008, 08:45PM

Registered Member #1225 Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253

Oh..I sure feel stupid!

Coronafix

Sun Apr 13 2008, 01:16AM

Registered Member #160 Joined: Mon Feb 13 2006, 02:07AM
Location: Melbourne, Australia
Posts: 938

Actually the setup is both primaries in parallel, one side connects to gap, the other side to the MMC.
So just swap the MMC with the spark gap in your diagram. This way the MMC is also in parallel with the primaries
but on the other side of the spark gap.

Kristian

Sun Apr 13 2008, 03:42AM

Registered Member #611 Joined: Wed Mar 28 2007, 11:40PM
Location: Hudsonville, Michigan
Posts: 79

I think I got it. Primaries in parallel, anti phased. I don't see why this wouldn't work. Can anyone confirm if this is correct?

hvguy

Tue Apr 15 2008, 04:46AM

Registered Member #289 Joined: Mon Mar 06 2006, 10:45AM
Location: Conroe, TX
Posts: 154

Yep, It's right. Provided your secondaries are wound the same direction it will work.

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