Building a QCW Tesla Coil

In this video, we explore how to build a quasi continuous wave or QCW Tesla coil. These devices are technically challenging to build but well worth the effort. They are basically DRSSTC Tesla coils with a ramped voltage input and with much longer on times compared with traditional DRSSTC Tesla coils. The first QCW Tesla coils were built by Steve Ward and refined by others such as Loneoceans. The idea for building QCW coils came from observations that VTTC staccato controlled Tesla coils with unfiltered mains input produced beautiful long straight sword-like arcs.

[@LabCoatz_Science]

Never thought I'd see a QCW video that wasn't just a demo! Congrats on the build man, hopefully I'll be able to join the QCW club someday!

[@BrianDhvTinkerer]

Thanks man! You’ll be in the “club” soon for sure! Your work is awesome!!

[@TeslaExplorer]

Yes the loop noise can get extremely tricky. Shortest possible connections for the main feedback loop of course and running the trunk through a high permanency ferrite ring just before feedback entry on the buck controller will do the trick. Getting the buck back into loop and adding a few extra foot to the spark! Ggy made note of this I believe, it's just not shown in his schematic. We greatly appreciate your explanations and illustrations. Big salute to you and Loneocean's both!

[@BrianDhvTinkerer]

Thanks a bunch. Yes that’s definitely true. I had long connections for the test setup which made the buckverter signal look coarse and messy 😁

[@Magneticitist]

I had to double check just to make sure and you indeed have this amazing ramp. I wish I could figure out how there is so little ripple. I also just noticed you have quite a bit of EMI filters which is funny because I recently bought a bunch and started snapping those things everywhere and saw quite a noticeable difference in the QCW.

[@All_Science]

Interesting! I was under the impression that the buck controller was needed for stable operation of the buck. Great vid btw!

[@BrianDhvTinkerer]

Thank you! It was fun. Will plan on doing a final build and follow up video soon!

[@ArcAngelTeslaCoil]

Love the video great output⚡⚡

[@BrianDhvTinkerer]

Thank you!!!

[@likha360]

awesome

[@m3sca1]

very nice work! perhaps that method can be used to drive a HHO cell with resonant efficiency... the ramp is a method Stan Meyer used and not many people have been able to replicate it. I have and it has to have a larger gap than everyone is usually using.

[@BrianDhvTinkerer]

Thanks really appreciate it!

[@Antagon666]

Great, now I want to build QCW...

[@BrianDhvTinkerer]

Thanks man! They are really interesting coils. I built 2 so far

[@inventorbrothers7053]

Awesome and informative video, thanks! Do you know why QCW tesla coils like a higher coupling coefficient for the primary and secondary? I'd imagine all tesla coils would, but is that not true?

[@BrianDhvTinkerer]

Interesting question. Seems like unlike DRSSTC, QCW coils are not really true DRSSTC- they are operating in upper pole mode

[@inventorbrothers7053]

@@BrianDhvTinkerer what is upper pole mode? Sorry that I'm unfamiliar with the terminology 😅

[@BrianDhvTinkerer]

@@inventorbrothers7053 basically a tesla coilin normal DRSSTC mode is a Resonant system operating with quarter wave across the coil with the bottom of the coil a zero point on the quarter wave and the top part of the coil the maximum part or voltage of the quarter wave of a full wave AC cycle. This resonant frequency gives maximal amplitude when tuning the secondary coil and top load combined. With a normal Tesla coil, as spark growth occurs, the capacitance of the top load effectively increases which decreases the resonanant frequency of the secondary. So typically in a DRSSTC situation, the primary coil resonance is set approximately 20% lower frequency than the secondary resonant frequency. As spark growth occurs, it drops the resonant frequency of the secondary so that it becomes identical to the primary resonant frequency. Then the coil is now in a double resonant situation. Massive amounts of energy can be transferred from the primary tank to the secondary coil as the impedances of the two systems become identical with spark propagation. This is sometimes known as spark “loading”. This is the true DRSSTC mode. The coupling between primary and secondary with DRSSTC needs to be low because of the way the energy is transferred. With a QCW system, things get much more complex. With a high coupling coefficient between primary coil and secondary coil, the two coils function together as a single resonant system in upper pole mode. The resonant frequency of both the primary and secondary coil jump into a different frequency, which is typically higher than both of the separate resonant frequencies which is known as the upper pole. My guess is that this is some kind of harmonic. However, when the two coils operate like this, there is maximal energy transfer. Because of the high coupling between the two coils, there are issues with secondary to primary strike. This is alleviated by ramping in the bus voltage essentially going from zero to voltage of around say 340 V. This results in a spark, which grows as the ramp increases. As the spark grows, the frequency of the Resonant system drops for both primary and secondary.

[@inventorbrothers7053]

@@BrianDhvTinkerer okay that makes a heck of a lot more sense. I didn't know before that the secondary LC circuit in a DRSSTC was tuned higher to account for resonant frequency drop during large spark discharges. That's actually brilliant. Thanks so much for your detailed response! 😁

[@michaelmule4582]

I was having the same issue with the buck modulator. I am going to run it straight from the generator later. Crossing my fingers there is no interference

[@BrianDhvTinkerer]

I was surprised how well it worked without the buckverter!

[@michaelmule4582]

Well, I ran some tests connecting the LC straight to the gate driver and I did get a ramp with minor interference. I attempted another build of the loneoceans buck modulator to no avail! It just doesn't work for me. I utilized the same setup as Magneticitist and so far its working well. @@BrianDhvTinkerer

[@johnsmith-oz3yz]

hi. how you can measure current primary just with one channel of scope? 🧐 can you explain to me please?

[@BrianDhvTinkerer]

Using 1000:1 step down transformer 1000A-->1A With 10 ohm burden resistor across the output of the transformer V= IR = 10 x1 = 10V. So a peak to peak voltage of 20V on the scope from the current transformer with this burden resistor would corresponding to 1000 A. A pk to pk of 10 V would be 500A etc

[@jonaoconnor8065]

Isn't that an H bridge?/

[@BrianDhvTinkerer]

Sure is- works very well

[@Milanlake]

Собери Квазинепрерывно волнистую двухрезонансно твердотельную катушку Теслы

[@dominickwest7558]

Jlaser did this in his thor hammer build

[@BackMacSci]

Thank you SciTube, this was very fun and informative! Did you use any other sources for help or lessons while building this, or just loneoceans site?

[@BrianDhvTinkerer]

Used a combo of loneoceans site, collaboration with ArcAngel, reading up on buck inverters, and just plain old experimentation 😂

[@youngk2495]

hello，I need a circuit diagram❤

[@BrianDhvTinkerer]

Based on www.loneoceans.com/labs/qcw/

[@tinkeringwithhighvoltage]

It’s very hard to build a qcw btw, I suggest you don’t waste money on that if you know nothing to begin with (not saying you know nothing)

[@BrianDhvTinkerer]

@@tinkeringwithhighvoltage that’s true! That’s what it makes it fun!

[@youngk2495]

@@tinkeringwithhighvoltage OK，agree with you

[@tinkeringwithhighvoltage]

@@youngk2495 from what he made, I estimated the costs to be somewhere around the 300-500usd zone (excluding all lab tools required for tuning and debugging), definitely not a great project for any low budget science fairs

[@user-ts8rp7wy2n]

Mettimi a posto i commodore malfunzionanti sono Biagio di balsamo e famiglia