Author Topic: Hydron's 160mm DRSSTC and topload current measurements  (Read 5517 times)

Offline Hydron

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Re: Hydron's 160mm DRSSTC and topload current measurements
« Reply #20 on: March 23, 2018, 12:59:28 PM »
The 2877 CTs have a bandwidth of something like 200MHz, so will not be the limiting factor. I was proposing to use a 35MHz CT for the base current measurement and a 2MHz CT for primary current (determined by what i have available - 2x2877, a 4100 and a 7800). I would be surprised if the CTs filter anything of interest out with a lower -3dB of 300Hz. I assume that you agree the best way to use 2 extra channels is to measure current?

Offline Uspring

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Re: Hydron's 160mm DRSSTC and topload current measurements
« Reply #21 on: March 23, 2018, 04:41:32 PM »
Yes, I agree. Primary current being even more interesting than base current, since it reflects the amount of power transferred to the secondary due to arc load and arc detuning.

300 Hz lower bandwidth looks ok. I guess that depends much on the loading resistor for your CT. It should be quite low.

Offline Mads Barnkob

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Re: Hydron's 160mm DRSSTC and topload current measurements
« Reply #22 on: March 24, 2018, 01:08:09 PM »
Great analysis that you got done there Uspring!

Regarding the phase shift / secondary impedance graph, what can be concluded on the loaded Q/impedance compared to the secondary Q/impedance?

As always the dynamic nature of arcs and our lack of plasma physic applied knowledge to it puts the models in the same regions as the existing ones :)
« Last Edit: March 24, 2018, 01:09:41 PM by Mads Barnkob »
http://www.kaizerpowerelectronics.dk - Tesla coils, high voltage, pulse power, audio and general electronics

Offline Uspring

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Re: Hydron's 160mm DRSSTC and topload current measurements
« Reply #23 on: March 24, 2018, 09:16:54 PM »
Thank you, Mads.

Wrt the primary tank answers are difficult. Secondary Q affects primary Q but primary Q is also dependent on the location of the secondary resonance. This frequency changes during the burst just as secondary Q. One idea is to design a coil in such a way, that everything is perfectly tuned at the point, when power requirement of the arc is largest.

Offline Hydron

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Re: Hydron's 160mm DRSSTC and topload current measurements
« Reply #24 on: March 25, 2018, 12:58:38 AM »
Yes, I agree. Primary current being even more interesting than base current, since it reflects the amount of power transferred to the secondary due to arc load and arc detuning.

300 Hz lower bandwidth looks ok. I guess that depends much on the loading resistor for your CT. It should be quite low.
For reference, these are what I am planning to use for the measurements:
http://pearsonelectronics.com/pdf/2877.pdf (x2, for topload measurements)
http://pearsonelectronics.com/pdf/4100.pdf (for secondary base current)
http://pearsonelectronics.com/pdf/7800.pdf (for primary current)

Still playing tourist in Australia right now, so haven't had a chance to look at your hard work yet sorry!

Offline Uspring

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Re: Hydron's 160mm DRSSTC and topload current measurements
« Reply #25 on: March 26, 2018, 04:38:41 PM »
@Hydron:

These CTs seem fine to me and they look like they have their resistors integrated. There is lot of inductance in the 2877, must be around 25mH.

I've taken a lot of time writing that up, so don't feel pressed yourself.

@Mads:

Using the equation

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

we have now some numbers for it at the point of maximum arc load:
Qsec=4, k=0.15, f=70kHz, fsec = 55 kHz (with arc loading), which
puts Qpri to about 80. That looks seriously too large. Either the coil is getting quite out of tune regardless of its low secondary Q or I've made some mistake about the secondary resonance frequency. The equation is quite sensitive to fsec. Hydron, did you measure secondary fres? I took your secondaries parameter from the posted Javatc results.




Offline Hydron

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Re: Hydron's 160mm DRSSTC and topload current measurements
« Reply #26 on: July 04, 2019, 11:39:39 PM »
So I have some new measurements to share, taken in Jan 2019. While there are some issues with them (less comprehensive than last time, and breakout from a second point on the toroid), I also have characterised the coil a LOT better (see javatc load file - all values should be accurate to within a percent or two based on physical and electrical measurements) and also measured both primary and topload currents.

Files are shared in the google drive folder below:
https://drive.google.com/drive/folders/1bDoH_atL-bCJeF0Slkl4aauANMzLPnha?usp=sharing

I may be able to add to and improve these in the next month or so as I will have access to the coil again (but not necessarily time to do much due to family commitments).

Offline Uspring

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Re: Hydron's 160mm DRSSTC and topload current measurements
« Reply #27 on: July 08, 2019, 09:59:49 AM »
Hydron, thank you for the new data. Currently I'm in downunders outback, where mobile net sort of lacks. I'll definitely scrutinize what you've got as soon as i'm back (end of July). Can't wait.  :)

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Re: Hydron's 160mm DRSSTC and topload current measurements
« Reply #27 on: July 08, 2019, 09:59:49 AM »

 


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