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Re: In search for a better PRIMARY

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Terry,

I dont think one needs the inductance nor di/dt if you just compute the volts per turn. If the primary cap fires with say 20KV into a 20 turn primary then the primary will have 1000 volts per turn. The volts per turn in the secondary (neglecting the distributed C) will be this value * kn. So if kn for that turn of the secondary is 0.20, then that turn will have 200volts induced into it (transformer action). The initial di/dt of the primary and secondary will fall out from the inductance of the primary and the inductance for that turn of the secondary (not sure how the magnetic coupling of that turn with others in the secondary affects this). Also, I'm not sure if whether the coil is or is not in tune will affect this initial voltage profile, but sure will affect subsequent profiles.

What I need to know in order to spice this is how to model a section of secondary coil where all the other sections are coupling into it as well as the primary. I believe Antonio gave you a program where there was a NxN coupling matrix to figure this out, but something to run in C and not a spice program.

Gerry R.

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>


Dest also looked into this:


But I don't think he did it quite right... The links are dead so I can't check now. But I think he did the di/dt wrong. If it was done right, I think his conclusion would be different ;-)))

I have seen miss-tuned coils do some very strange things. Fat 1 foot arcs from the lower six inches of the secondary to the primary... Primary to secondary arcs blowing holes though 1/4 inch G-10... And of course racing arcs... I think all this will be explained in a few days now :-))))))



At 10:17 PM 8/13/2006, you wrote:
Hi Terry,

Yes, I think I have enough info to compute the initial voltage profile. It will be interesting to also add the wave propagation to the model to see what happens over time and subsequent half cycles. My guess is that the problem is more complex than the initial voltage profile but modeling the secondary into managable number of segments may be a reasonable way to shed some light. Maybe we can share ideas on this and the modeling and I can proceed. You have a very intuitive perspective.

Gerry R.

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Gerry,

You may be able to resolve the racing arc issue now.

You know the di/dt of the primary coil.
You know the coupling to any arbitrary ring along the secondary.
You know the inductances.
You have a well known coil situation that is apparently close to the edge to study.

If we assume the racing arc occurs in say the first 1/4 cycle (probably in the first micro second!), then the other resonances and harmonics have no effect since they have not had time to setup yet.

Thus, the voltage gradient along the secondary in the first instant of firing is now taking into full account the primary to secondary geometry and coupling...

MandK can be set up to find the data in a single run and you can modify the MANDK.INI file for further control. You can just make the high increment the same as you coil section increment to calculate the right data directly.


The coupling/length output data file can probably be imported to a spreadsheet.

Thus, you should be able to graph the Voltage/UnitLength along the secondary for any primary to secondary configuration in the first instant the gap fires and from there determine if that is causing the racing arcs.

If one cleans the gaps, the initial di/dt in the primary coil my increase. Thus your gap cleaning may indeed have increased the change for secondary racing arcs.

I have always felt that the racing arc issue was a matter of pure transformer action. So maybe you can prove me right :D



At 11:53 PM 8/9/2006, you wrote:
Hi All,

Terry just put a writeup I did on my investigations using JavaTC into what may be a better primary concept. It is located at:


If the idea works out, it may allow for higher coupling without inducing racing arcs.

Please feel free to comment or criticize (hopefullly constructively) and If anyone is willing to try the idea, I would be willing to consult.

Gerry R