Re: Large DRSSTC: choosing secondary impedance
Dr. Slack, Mon Apr 21 2014, 08:04PM

To an engineering approximation, 70k *is* 50k, just like secondaries have 1000 turns, +/- 3dB

Re: Large DRSSTC: choosing secondary impedance
HV Enthusiast, Mon Apr 21 2014, 10:20PM

Can you provide more information regarding your failure?

Looks like you have a single point failure on your secondary which could have been caused by:

1. Faulted wire - kinked wire, overlapped wire, etc....
2. Too much coupling which caused an arc over at a weak point in your epoxy etc...
3. Dust / debris on your secondary causing an arcing problem (I once had a moth land on my secondary coil causing it to arc at that point killing the secondary)
4. Bad grounding (this can cause your secondary peak voltage to occur somewhere other than the top)
5. Improper primary to secondary spacing - voltage breakdown

Re: Large DRSSTC: choosing secondary impedance
Kizmo, Tue Apr 22 2014, 04:14AM

This coil is has relatively loose coupling, around .165 and there has *never* been single flashover over the period of 2 years i have run this thing. Failure started as turn to turn arcing ~100mm from the bottom end of the coil.

Im not too concerned about why it failed. When the failure happened we were ripping really loud and bright 3...4x secondary winding length ground strikes at nearly 15kW (yes, thats DC power, 28kVA..)

I suspect the failure has something to do with this

As interesting experiment im planning to build another secondary of same dimensions that has lower impedance, less turns and space winding at least the bottom end of the in hopes of adding more insulation between turns.

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Tue Apr 22 2014, 10:25AM

I agree there is the possibility of some sort of "whiplash effect" where a really hard ground strike launches a travelling wave down the secondary. It may well be reflected from the bottom causing a buildup of voltage there. I think the best solution is to include some sort of impedance in the ground strike circuit.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Tue Apr 22 2014, 11:45AM

Since the primaries magnetic field is strongest at the bottom of the secondary, the voltage induced in the secondary might cause a particularly strong electric field near the bottom. Spacing the windings at the bottom of the secondary probably helps since it reduces the electrical field there and also improves inter winding insulation.

A side effect of this is, that it will reduce coupling.

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Tue Apr 22 2014, 12:16PM

The voltage profiles in a DRSSTC are different to the ones calculated by TSSP/GeoTC, which assumes spark gap operation, exciting both resonant modes equally.

The voltage profile in a DRSSTC depends on which mode is excited. The lower resonant frequency gives a "convex" profile with a high E-field in the vicinity of the primary, as described by Uspring above. The upper one does the opposite, it gives a "concave" profile with a weaker E-field near the primary and a stronger one further up the secondary.

I proposed this years ago and Richie Burnett verified it by experiment. It's still a mystery to me how the primary manages to transfer energy into the secondary when the mutually induced voltage is opposing the self-induced one, but it's a fact that it happens.

Re: Large DRSSTC: choosing secondary impedance
Kizmo, Tue Apr 22 2014, 01:59PM



This was filmed after I realized the coil was not worth of repairing. It may look like it but there was no primary-secondary strikes, just more or less shorted turns arc welding each other.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Tue Apr 22 2014, 02:25PM

Steve wrote:

It's still a mystery to me how the primary manages to transfer energy into the secondary when the mutually induced voltage is opposing the self-induced one, but it's a fact that it happens.

Average power transfer is proportional to the sine of the angle between primary and secondary current. At the lower pole it's closer to zero and for the upper pole closer to 180 degrees. It's best to push a swing hardest, when it's at the bottom

Looking at the video, it seems though, that ground strikes are the culprit.

Re: Large DRSSTC: choosing secondary impedance
Goodchild, Wed Apr 23 2014, 03:34PM

This subject is also of interest to me. Because I too run coils with high impedance. My large coil for example has an impedance of near 80K at its 41KHz resonant frequency (this is without spark loading).

302.7mH secondary impedance (calculated)

Without spark loading at 41KHz it’s 78K

With spark loading at 31KHz it’s 58.8K

So after the secondary is loaded it drops down a lot, however when we get ground strikes I imagine this loading drops to nothing (because capacitance drops and frequency goes back up) and the impedance rises back up to near 77k. Am I correct in thinking this?

To my point, ever sense we have started using a counterpoise ground I have noticed that the coil is more prone to flashing over and burring up secondareis. I thought this was just a coincidence but your guy’s comments have made me think otherwise.

The counterpoise ground helps to reduce radiated interference (lower impedance path to ground) however could it be a problem when dealing with ground strikes?

I’m also curious to where the magic 50K keeps coming from?

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Wed Apr 23 2014, 03:57PM

I recommended the "magic 50k" years ago. I worked it out from Terry Fritz's streamer loading models, and the assumption of a loaded Q of 10. It also agreed with the better performing coils at that time.

Re: Large DRSSTC: choosing secondary impedance
Hydron, Thu Apr 24 2014, 01:40AM

Eric - sounds like testing Arc Attack's inductive breakout point idea might be worthwhile if you're burning up secondaries too.

I may be able to do some arc measurements to try and increase the understanding of what happens with ground strikes etc. I've got a PC based scope which can talk over wifi, so should be able to battery power it and stick it on the topload to get realtime data on arc impedance. It also has a few megasamples of segmentable memory, which is handy to capture a good burst.

No guarantees if/when I can do any measurement, and how applicable it would be to larger coils than my 160x700mm, but it's certainly an interesting topic.

Re: Large DRSSTC: choosing secondary impedance
Mads Barnkob, Thu Apr 24 2014, 09:23AM


This is a great topic, my own secondary for my large DRSSTC is around 56K.

Is there any online documention to arc attacks inductive break out point, searching on google did not turn anything up for me since its so generic words.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Thu Apr 24 2014, 09:35AM

Steve Conner wrote:

I recommended the "magic 50k" years ago. I worked it out from Terry Fritz's streamer loading models, and the assumption of a loaded Q of 10. It also agreed with the better performing coils at that time.

Can you give some details on your thoughts at that time? I wonder if this rule can be stretched by other design parameters such as primary inductance, frequency, coupling, choice of poles, high power versus low power etc.

Hydron wrote:

I may be able to do some arc measurements to try and increase the understanding of what happens with ground strikes etc. I've got a PC based scope which can talk over wifi, so should be able to battery power it and stick it on the topload to get realtime data on arc impedance. It also has a few megasamples of segmentable memory, which is handy to capture a good burst.

I'd be very interested in hearing about these kinds of measurements. I've done some of these with a mini DSO on top of the coil but have never looked at ground strikes.

Re: Large DRSSTC: choosing secondary impedance
Kizmo, Thu Apr 24 2014, 10:25AM

Now this is even more interesting, this run was first with both counterpoise ground (1x2m metal mesh on ground) and ground rods. It may or may not have something to do with this..

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Thu Apr 24 2014, 10:28AM

It is interesting indeed! Maybe a poor, high impedance ground absorbs the "whiplash" instead of reflecting it.

Re: Large DRSSTC: choosing secondary impedance
Hydron, Thu Apr 24 2014, 10:52AM

These question are why I'm gonna have a crack at some measurements - topload measurements been done before, but apparently on more of a single-shot basis, rather than looking at a burst, or ground strikes vs normal streamer hits etc. Might have to rig up a counterpoise and include that too. My advantage in this case is that I can grab the data while running the coil, rather than set up a mini DSO for a single capture.

I'm about to do some testing on getting 5.8GHz wifi through a faraday shield (~5cm holes should do the trick), if that works then I'll set up the coil tomorrow and have a go at getting real data. I think I'll try sticking the router only on the topload first though, really don't want to pop the scope if there is an issue!

Edit:
Maybe it's time for someone to measure ground impedance too! (at TC frequencies obviously). If it turns out to be anywhere near the secondary impedance then the increased-secondary-destruction-with-counterpoise phenomenon would make a lot of sense, as a terminated transmission line wouldn't have a big reflected wave causing high voltage at the bottom of the secondary.

Re: Large DRSSTC: choosing secondary impedance
Mads Barnkob, Thu Apr 24 2014, 11:34AM


Here are some interesting papers on earth resistance, impedance, skin depth etc:
Theory but some missing pictures:


Lots of practical measurements and data in tables for TC frequencies - seems like a newer version of the same:

Seems similar as the above, but in Italian:

Another ground vs lightning study: ,d.bGQ&cad=rja

Measurements by a HAM operator:

Re: Large DRSSTC: choosing secondary impedance
Uspring, Thu Apr 24 2014, 11:39AM

I've used Wards values from
They amount to about 0.1pF/cm and 2.6mH/cm for his secondary. From the transmission line equations that results in

v=1/sqrt(L*C) i.e. about 600km/s,

which is about what he gets. For a perfect termination of pulses running down the secondary you need a resistance of

R=sqrt(L/C) i.e. about 160k

This is seriously too large, considering the several amps that are flowing out of the base. The only way to achieve proper termination is to do it only for high frequencies, i.e. an induction at the base essentially shortcutting TC frequencies paralled by a resistor.
I wouldn't expect a whiplash anyway, since a good grounding of the base would just reflect the pulse without increasing the amplitude.

Re: Large DRSSTC: choosing secondary impedance
Hydron, Thu Apr 24 2014, 12:15PM

Yeah, 160k is way too big. Just did a quick sweep of the ground in my (fairly damp) back yard, between a shallow spike (~5cm) and either a deeper spike a couple of meters away (still not very deep, only about 30cm) or mains earth, or both. Technique was essentially the same as the HAM operator did in Mads Barnkob's last link (at a quick glance, results look very similar too, despite very different distance). Quick answer: about 1k ohm. Results are below, the file names indicate which test is which:



As for the transmission line amplitude stuff, you can indeed get a voltage increase of 2x upon reflection, but only for an _open_ circuit transmission line, a short circuit should reflect the inverse of the incident wave (adds up to 0 at the short). I haven't though too hard (let alone done any modelling) about the applicability of TL theory to the secondary though - might be looking at this completely incorrectly.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Fri Apr 25 2014, 09:14AM

I haven't though too hard (let alone done any modelling) about the applicability of TL theory to the secondary though - might be looking at this completely incorrectly.

Paul Nicholson has done extensive work around secondary modelling.
My impression from that is, that a transmission line approximation is roughly correct. His analysis is much ore detailed, though.. If you drive your secondary with frequencies a lot above the fundamental, you'll observe resonances corresponding to higher transmission line modes.

Wrt to the optimal secondary impedance:
The power transfer to the secondary depends on the arc (resistive) load. For a given primary current it has a max at a specific arc resistance. If primary and secondary resonate at the same frequency this max is reached approximately, when Qsec = 1/k. Qsec is the ratio of arc resistance and secondary impedance. Arc resistance depends very much on how much power you put into the arc and will decrease with more power. Typical values are maybe around a few hundred kohms, so the optimal secondary impedance would be k times a few hundred kohms, i.e. maybe 50k. I tend to believe, that a lower value might work somewhat better particularly for high power coils.

Since the arc detunes the secondary to a varying extent, the initial assumption, that primary and secondary resonate at the same frequency cannot really be upheld. Optimally this condition should be reached at the end of primary rampup.

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Fri Apr 25 2014, 12:21PM

Interesting. Since arc load is a function of power transfer, and power transfer is a function of arc load, it sounds as if the loaded Q of the secondary would tend towards 1/k as the drive level was increased.

It would follow that coupling would ultimately limit the power throughput of the system: no amount of extra primary current could make up for a lack of coupling.

How does primary Q enter into the equation? I always tried to design so that both primary and secondary would have a loaded Q of 10, but I don't have an intuitive feel for how the load on the secondary affects the Q of the primary.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Fri Apr 25 2014, 01:55PM

Whether there is an upper limit to power througput depends on how much the arc resistance changes with power. For no change of arc resistance, the power throughput would be proportional to Ip^2.

For primary Q I have 2 equations for the limits of high and low arc loads. They are in terms of the primary loss resistance, from which you can calculate the primary Q:

Rp = w°2 * Lp * Ls / Rarc, for large Rarc

and

Rp = k^2 * Lp / Ls * Rarc for small Rarc.

In essence you always need to take the lower ones of the Rps. Or better, think of both Rps in parallel. The first equation depends sensitively on tuning. And these equations hold only for ZCS.

Re: Large DRSSTC: choosing secondary impedance
Goodchild, Fri Apr 25 2014, 03:19PM

Wow you guys are smart! So if I have this straight assuming we treat this system as a transmission line, we are essentially dealing with a series circuit that includes Zsec, Zarc, and the impedance of the earth ground Zgnd.

Now assuming we have no ground strikes Zarc stays the same (with a constant power that is). As soon as we get a ground strike Zarc drops off significantly. This would then prompt a large change in current, but because current can't change instantaneously threw Zsec this current has to propagate across the secondary.

So with classic transmission line theory we want to match the terminating impedance Zgnd to the secondary circuit impedance Z sec. Using Udo’s example 160K would be the terminating Z.

What I’m not fully understanding, why is 160K to large? Is this because of practical implementation? ie your earth ground would never be this large?

Re: Large DRSSTC: choosing secondary impedance
Hydron, Fri Apr 25 2014, 05:44PM

160k is too large because any practical ground is way less (mine was ~1k). Even if you had really dry soil or something, you couldn't run a TC with a ground that bad, the amps of secondary current would produce 100s of kV across it.

Uspring: How did you go about analyzing your arc measurements? I've got some preliminary data for my coil, but the only analysis I've done so far was using the scope maths functions (not yet sure how to deal with the 2 megasample files!).

A quick look at what I did manage suggests arc impedance drops off precipitously with ground strikes (to sub 50K ohm, clamping toroid voltage to <100kV), but I'm not willing to put hard numbers to anything yet.

Tonight I'll try and improve my setup and get some better data, along with some simultaneous camera exposure. Hopefully I can get the scope to let me only capture the coil on-time, which should make the data more manageable and let me use higher sample rates. Will post it all (probably in a new thread) once I've got something I'm happy with.

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Fri Apr 25 2014, 07:05PM

160k is too large because it would damp the desired resonance of the secondary coil and eat up all the power that is supposed to go into sparks.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Fri Apr 25 2014, 07:30PM

I measured current between secondary top and toroid and between toroid and breakout point. From this you can derive top voltage and arc current. The DSO can dump txt files with the ADC readings, which I imported to a spreadsheet. Beyond voltage and current magnitudes also the phase between them is interesting. To extract the phase, I wrote a little program which calculated the times of zero crossing by interpolation.

Re: Large DRSSTC: choosing secondary impedance
Hydron, Fri Apr 25 2014, 10:47PM

Uspring: sorry, I should have been a bit clearer.
I know what to do (find the difference between the two measured currents to get topload charging current. integrate to get topload voltage, use I and V and the phase to look at streamer impedance), but not the best way how to do the analysis.
I haven't touched matlab etc for years, and I can't import 2 megasamples (!) into a spreadsheet, so I was hoping you had a quick and easy answer I could steal.

I can actually use the scope software to do the integration, scaling, subtraction etc, but I can't get the instantaneous phase or magnitude out of it without passing the data off to matlab. I'd also like something easier to make the requisite pretty graphs with.

Edit: I had posted some scope captures here, but I no longer trust them - the only low value resistors (for the current shunts) I could find last night were wirewounds which turned out to be more inductive than I expected, so I'm gonna get some better data before sharing.

Re: Large DRSSTC: choosing secondary impedance
Intra, Mon Apr 28 2014, 08:50AM


I had same issue. That's not an impedance problem. It can be a wire's coat. In some cases, if source wire for secondary is old, epoxy coating may crack under the influence of time. Therefore reduced dielectric breakdown strength and produce winding electrical breakdown. Also, common secondary coating may have been not large enough for sufficient dielectric strength.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Mon Apr 28 2014, 09:41AM

Here is an equation, which describes primary Q within a simple TC model, that neglects any losses except loading by the arc.

Qpri = Qsec/k^2 * (1 - f^2/fs^2)^2 + 1/(k^2 * Qsec)

f is the frequency the coil is running on and fs the secondary resonance. The equation is exact for those f, for which there is zero current switching, e.g. at the poles.
Generally it is an advantage to have a low Qpri since it means a fast transfer of energy in the primary tank to the secondary. Otherwise you would build up a lot of energy in the primary tank by the driver without it getting to the secondary. Also, a large amount of energy in the primary tank will cause large losses in it due to copper and MMC resistance.

Qpri gets minimal with respect to f, if f=fs. If primary and secondary resonances are at the same frequency and the coil is run e.g. at the lower pole, then f = fs/sqrt(1+k). The above equation then simplifies to:

Qpri = Qsec * (1+k)^2 + 1/(k^2 * Qsec)

Detuning, i.e. choosing primary and secondary fres different, will in general increase the first term considerably. This can be an advantage for some coils, since it allows to match the drivers voltage and current capabilities to the primary tank.

The equations also show a minimum for certain Qsecs. This gives an idea on how to choose secondary impedance, since Qsec is the ratio of arc load resistance to secondary impedance. The change of tuning and also the change of the arc load resistance during a burst makes this difficult.

Re: Large DRSSTC: choosing secondary impedance
Kizmo, Mon Apr 28 2014, 10:37AM


Im not blaming impedance for my secondary failure. I used premium quality double enameled high temp wire, pretty much best stuff money could buy from local motor winding shop. 22kg reel was like 500euros.

Reason why i started this thread was just to find out if anyone has experimented with different impedance secondaries and got performance gains. I think my next secondary will space wound for added insulation and kind of low impedance, around 35kOhm at unloaded f0.

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Mon Apr 28 2014, 01:11PM

My OLTCs all had >100k Zo and they never quite performed as well as I hoped.

Also, I think I remember Richie Burnett saying that he tried 22k and 50k on his sparkgap coil, and 50k gave much better results. Maybe with more power behind it, the opposite might be true.

For Odin I went for a Zo of about 50k according to the received wisdom, but the stubby secondary and conical primary give a coupling of about 0.225 which is considerably higher than other DRSSTCs I've seen. Got to explore the parameter space a bit more

Re: Large DRSSTC: choosing secondary impedance
Uspring, Mon Apr 28 2014, 01:59PM

The equations describe really only a steady state situation and are therefore guidelines only for long burst DRSSTCs. They don't capture the dynamics of OLTCs or similarly SGTCs. Possibly short duration arcs may also have a higher resistance.

The best thing you can do and you've already done that, is to tune primary low and run at the upper pole. That will result in an operating frequency very close to the secondary resonance and consequently reduce Qpri.

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Mon Apr 28 2014, 02:38PM

Interesting! I've been doing this for years, but I think Steve Ward recently rediscovered it.

It is only possible with a PLL driver, because a feedback driver will always snap to whichever pole has the higher value of Qpri, but a PLL will lock to whichever is closest to the starting frequency.

I've noticed that under some circumstances, the upper pole can disappear completely: the phase doesn't swing through zero any more. Can this be seen as a case of Qpri just getting too low?

Re: Large DRSSTC: choosing secondary impedance
Uspring, Mon Apr 28 2014, 03:57PM

At light loads there are 3 ZCS frequencies, the 2 poles and one in the middle. If Qsec drops below 1/k, there is only one left. I'm surprised, that the PLL won't find that. Maybe that is, because there might be a frequency jump from the pole to the left over ZCS frequency.

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Tue Apr 29 2014, 09:07AM

I think although the phase doesn't swing through zero, there can still be an inflection point in it and the PLL can sometimes get stuck there. Most of the time it seems to work right, but I have seen it sometimes act funny under conditions of heavy streamer loading with the primary detuned very low.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Tue Apr 29 2014, 11:01AM

Yes, exactly. Under the conditions you describe, a region of minimum phase shift between primary voltage and current appears, where the minumum is not zero. A PLL will lock onto that.
I've seen a simulation circuit from Steve Ward, where he starts off for a few cycles generated by an external frequency source located at the upper pole. Then he changes over to switching at zero current. In the simulation, that seemed to work and might be more robust wrt to this problem. I dunno, whether he does it this way in his real circuits.

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Tue Apr 29 2014, 12:00PM

I think Steve uses a digital PLL based on a microcontroller now and he seems to be very happy with the performance.

Nowadays I am trying to promote research into FPGA-based driver hardware that would be powerful enough to run any conceivable algorithm. A PLL, a digital simulation of the popular phase lead feedback driver, some combination of the two, or something completely new that nobody has even thought of yet, like an adaptive driver that changes strategy dynamically based on streamer loading.

FPGAs are getting cheaper and more accessible every day, but soldering the !$$**? things to a board is still an issue.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Tue Apr 29 2014, 12:29PM

A smart controller would be nice
I think I made an error in my previous post. A phase shift between primary current and voltage should drive the PLL into the right direction until the phase changes sign. A minimum shouldn't hurt. I'm still mysified.

I wonder about the range of your PLL. Does it have a PI feedback?

Edit: Sorry for getting a bit OT here.

Re: Large DRSSTC: choosing secondary impedance
Steve Conner, Tue Apr 29 2014, 12:49PM

Yes, it is a type 2 PLL using an opamp integrator for the loop filter.

There is also a limit on the VCO range and I set this to exclude the lower pole. I guess it's possible that under very heavy streamer loading, the remaining ZCS frequency could be similar to the unloaded lower pole frequency.

To put things in perspective, my PLL driven coil managed a 59" ground strike from a 13" tall resonator.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Tue Apr 29 2014, 03:01PM

The remaining ZCS frequency is close to primary fres. You probably excluded that.

Can't wait to see Odin throw sparks.

Re: Large DRSSTC: choosing secondary impedance
Kizmo, Fri Jul 25 2014, 04:12AM

Allright guys.

New space wound secondary is now finished and measured. Here are some numbers:

- 1300 turns
- 93.4mH calculated
- 0.67mm wire
- 0.58mm between turns

Measured resonant frequency without "streamer" was 63.3kHz. Calculated whole system capacitance is 67.67pF and reactance at resonance 37.1kOhm

With 4 meter metal rod as fake streamer the resonance peaked at 56.3kHz. From there i get 85.544pF capacitance and reactance of 33kOhm


Now i just need to wait ~1 month for darker nights. Right now its as dark as it gets.

Re: Large DRSSTC: choosing secondary impedance
Mads Barnkob, Mon May 09 2016, 12:22PM

I wanted to elaborate on the small tables that you often find about width:ratio to power levels for Tesla coil secondaries.

I assumed only secondaries of ratio 4:1 to 6:1, with different wire sizes and always a toroid topload that follows the rule of major diameter = secondary winding length, minor diameter = secondary coil diameter.

So far it does not contain any surprises, the general design thumb rules does however land around 50K.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Wed May 11 2016, 08:52AM

If you "magnify" a secondary, e.g. double all dimensions, inductance and top load will double, resonant f will be halved and Zsec will remain constant.

I believe, Qsec, i.e. secondary Q with arc load, should remain equal for different coil sizes. Since arc load increases for more power, Zsec should decrease (somewhat) for higher power coils. A badly chosen Zsec can be compensated for to some extent by more primary turns. That involves longer rampup times and more losses in the primary winding, though.

Re: Large DRSSTC: choosing secondary impedance
Kizmo, Wed May 11 2016, 01:42PM

It is hard to say if the new secondary somehow runs better than the old in terms of power vs spark output but the heavy epoxy coating and space winding did make it very resistant to flashovers and racing sparks. I have had lot of them while experimenting and so far there is absolutely no damage at all :)

Oh btw, here is a small video i made a while ago about how the coil was made:

Re: Large DRSSTC: choosing secondary impedance
Mads Barnkob, Tue May 17 2016, 08:48AM


I was looking for a difference in desired impedance, not to seek out the optimal design, but to discover the boundaries of "usable" secondary coil construction.

I would like to add the loaded secondary Q, maybe a few different loads, then compare those Qs to a extensive list of q=1/k for k between 0.1 to 0.25 or so, for each of the listed configurations. Does it make sense?

"badly" chosen as you state, is only in regard to designing low impedance primary circuits for highest possible primary peak current in the shortest amount of time, so the sheet might also have to take into account(separate files to avoid additional 150 tabs) if you build low impedance, high current, short ontime expensive coil systems or high impedance, lower current, long ontime less expensive coil systems.

Re: Large DRSSTC: choosing secondary impedance
Uspring, Tue May 24 2016, 03:06PM

Mads Barnkob wrote:

I would like to add the loaded secondary Q, maybe a few different loads, then compare those Qs to a extensive list of q=1/k for k between 0.1 to 0.25 or so, for each of the listed configurations. Does it make sense?

Arc loads used to derive secondary Q are unknown territory. They change with power input and also during arc growth. Hard to tell, what is sensible without any measurements.