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Registered Member #1799
Joined: Thu Nov 06 2008, 02:20AM
Location:
Posts: 23
1000 Turn 3.5"x20" 25AWG PVC secondary 4"x14" Toroid 10 Turn 32* primary (it was tuned in, i adjusted it several times (even adding an 11th turn that ended up not being used)) I had very high coupling, occasional racing spark. I adjusted it and it seemed like best spark was at high coupling. Maybe a little lower coupling would be better?
-----------------------------------------
----------- Secondary Outputs: -----------------------------------------
----------- 304.32 kHz = Secondary Resonant Frequency 90 deg° = Angle of Secondary 20 inch = Length of Winding 50 inch = Turns Per Unit 0.0021 inch = Space Between Turns (edge to edge) 916.3 ft = Length of Wire 5.71:1 = H/D Aspect Ratio 29.4161 Ohms = DC Resistance 26174 Ohms = Reactance at Resonance 0.89 lbs = Weight of Wire 13.689 mH = Les-Effective Series Inductance 14.656 mH = Lee-Equivalent Energy Inductance 14.349 mH = Ldc-Low Frequency Inductance 19.981 pF = Ces-Effective Shunt Capacitance 18.662 pF = Cee-Equivalent Energy Capacitance 31.543 pF = Cdc-Low Frequency Capacitance 5.3 mils = Skin Depth 15.216 pF = Topload Effective Capacitance 102.2592 Ohms = Effective AC Resistance 256 = Q
-----------------------------------------------
----- Primary Outputs: -----------------------------------------
----------- 277.63 kHz = Primary Resonant Frequency 8.77 % high = Percent Detuned 27 deg° = Angle of Primary 23.56 ft = Length of Wire 3.91 mOhms = DC Resistance 0.222 inch = Average spacing between turns (edge to edge) 0.616 inch = Proximity between coils 1.52 inch = Recommended minimum proximity between coils 23.477 µH = Ldc-Low Frequency Inductance 0.0114 µF = Cap size needed with Primary L (reference) 0.51 µH = Lead Length Inductance 90.062 µH = Lm-Mutual Inductance 0.155 k = Coupling Coefficient 0.128 k = Recommended Coupling Coefficient 6.45 = Number of half cycles for energy transfer at K 11.44 µs = Time for total energy transfer (ideal quench time)
-------------------------------------------
--------- Transformer Inputs: ------------------------------------------
---------- 120 [volts] = Transformer Rated Input Voltage 15000 [volts] = Transformer Rated Output Voltage 60 [mA] = Transformer Rated Output Current 60 [Hz] = Mains Frequency 120 [volts] = Transformer Applied Voltage 0 [amps] = Transformer Ballast Current 0 [ohms] = Measured Primary Resistance 0 [ohms] = Measured Secondary Resistance
--------------------------------------
-------------- Transformer Outputs: -----------------------------------------
----------- 900 [volt*amps] = Rated Transformer VA 250000 [ohms] = Transformer Impedence 15000 [rms volts] = Effective Output Voltage 7.5 [rms amps] = Effective Transformer Primary Current 0.06 [rms amps] = Effective Transformer Secondary Current 900 [volt*amps] = Effective Input VA 0.0106 [uF] = Resonant Cap Size 0.0159 [uF] = Static gap LTR Cap Size 0.0277 [uF] = SRSG LTR Cap Size 166 [uF] = Power Factor Cap Size 21213 [peak volts] = Voltage Across Cap 53033 [peak volts] = Recommended Cap Voltage Rating 3.08 [joules] = Primary Cap Energy 512.4 [peak amps] = Primary Instantaneous Current 43.4 [inch] = Spark Length (JF equation using Resonance Research Corp. factors) 19.6 [peak amps] = Sec Base Current
-----------------------------------------
----------- Rotary Spark Gap Inputs: ------------------------------------------
---------- 0 = Number of Stationary Gaps 0 = Number of Rotating Electrodes 0 [rpm] = Disc RPM 0 = Rotating Electrode Diameter 0 = Stationary Electrode Diameter 0 = Rotating Path Diameter
----------------------------------------
------------ Rotary Spark Gap Outputs: -----------------------------------------
----------- 0 = Presentations Per Revolution 0 [BPS] = Breaks Per Second 0 [mph] = Rotational Speed 0 [ms] = RSG Firing Rate 0 [ms] = Time for Capacitor to Fully Charge 0 = Time Constant at Gap Conduction 0 [µs] = Electrode Mechanical Dwell Time 0 [%] = Percent Cp Charged When Gap Fires 0 [peak volts] = Effective Cap Voltage 0 [joules] = Effective Cap Energy 0 [peak volts] = Terminal Voltage 0 [power] = Energy Across Gap 0 [inch] = RSG Spark Length (using energy equation)
---------------------------------------
------------- Static Spark Gap Inputs: ------------------------------------------
---------- 8 = Number of Electrodes 0.875 [inch] = Electrode Diameter 0.29 [inch] = Total Gap Spacing
-----------------------------------------
----------- Static Spark Gap Outputs: -----------------------------------------
----------- 0.041 [inch] = Gap Spacing Between Each Electrode 21213 [peak volts] = Charging Voltage 20373 [peak volts] = Arc Voltage 34185 [volts] = Voltage Gradient at Electrode 70252 [volts/inch] = Arc Voltage per unit 96 [%] = Percent Cp Charged When Gap Fires 7.625 [ms] = Time To Arc Voltage 131 [BPS] = Breaks Per Second 2.84 [joules] = Effective Cap Energy 551998 [peak volts] = Terminal Voltage 373 [power] = Energy Across Gap 46.3 [inch] = Static Gap Spark Length (using energy equation)
Registered Member #1127
Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139
Your capacitance is small - so this also requires more turns as well. Use a top-load and you should see a big improvement in output performance. I had similar problems with my 4" X 40" PVC coil using 3/8" tubing. I ran 12 kV 120mA and at first light my output was really bad at turn 8. So I tapped out to the far end of the primary turn 12 placed my top load on the secondary and - PRESTO --- More turns on the primary side mean lower resonant frequency. I had made the mistake before of saying the opposite fact - I was wrong. Lets move on.
Registered Member #1799
Joined: Thu Nov 06 2008, 02:20AM
Location:
Posts: 23
no, more turns would mean a lower Fres. Also, adding more top-load would require me to use more turns.
Fres = 1/(2*pi*sqrt(LC))
Maybe there is just some kind of "magicalness" I'm missing. I'm just not sure what!! I picked the size capacitor I did because it showed the most power throughput, but static gap operation may just be too chaotic to effectively model.
Coincidentally, the LTR value for a 240bps synchronous rsg is 13.8nF. Maybe I should try that. With the static gap, microsim says I should get a break rate of 120bps and of course the high loss of a static gap. So with the rsg, I get 2x power throughput and a "less lossy" tank circuit. 2x20" puts me closer to the predicted 43" sparks...
Registered Member #1127
Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139
Add more turns to the primary and you'll see an improvement in performance. Do nothing and you'll keep having performance problems. My 4" TC ran 1500 watts - I increased my sparks by over 20" - making my total length 50" - with a little bit of fiddling later I got to my target of 60". This is how it is done. Primary turns / physical size of the coil directly relates to resonant frequency. A secondary wound with a higher AWG on a small form number means that automatically you will have a higher resonant frequency. A larger amount of turns on the primary helped me achieve maximum performance. Without a top load you won't get the ideal output.
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Nick -
I agree that you should be able to achieve better than 20" output from your system, but optimizing a coil's performance frequently takes a lot of experimentation and incremental changes. First, a few questions about your coil:
1. Is your "20 inch" output the free air (streamer) discharge length, or discharge length to a grounded target? 2. Are you absolutely sure that BOTH legs of BOTH NSTs are developing full output? How did you verify this? 3. Are the outputs of your NSTs properly phased? How did you verify proper phasing? 4. Please describe your tank capacitor: MMC or something else? Construction, dielectric material, etc. How did you determine the exact ".0137uF" value? 5. What gage wire is used to connect your spark gap, tank cap, and primary coil? 6. Please describe your 8-segment spark gap: design, electrode material, electrode shape, etc 7. What are you using as a secondary ground? 8. How is your 4" X 14.7" toroid constructed? What material is it made from?
Is there any way you can post some detailed photos of the coil's construction? Frequently, this gives the best insight into design or construction problems.
Registered Member #1127
Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139
Check my vids out here:
I find it rather amusing that the TC calculator gave me all kinds of tuning formulas to follow. I found that in general I had to add several more turns onto my primary to get the ideal output. Just throwing it out to you. It has not been my experience that the primary tuning has been anywhere close to accurate for me.
I'd also be pretty cautious about your NST. 20" discharge is pretty small for nearly 1000 watts of power output. I'd check the output of the transformer just to be safe. Do you have access to a multimeter?
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
MOT Man -
Sorry, but your statement that "You need at least 15 turns to get a coil up to resonance with 1/4" tubing" is, well, completely ludicrous.
A Tesla coil can be designed (and operated) with a 1-turn primary, or with a 30-turn primary. The critical factor is that the primary and secondary circuits have the same resonant frequency during operation.
You are also confused about a few other issues:
1. "More turns mean higher resonant frequency, usually." This is 100% wrong. Simply adding more turns to either a primary or secondary coil will always DECREASE the resonant frequency, period. There is no "usually" involved. If you throw a rock vertically up into the air, it will always come back down, period.
2. "A secondary wound with a higher AWG number means that automatically you will have a higher resonant frequency ~ generally". This is 100% wrong. The "higher" (larger) the AWG number is, the smaller the wire diameter, and the larger the number of turns per a given unit of secondary coil length. The larger the number of turns, the LOWER the resonant frequency, period. Again, there is no mysterious "generally" factor involved.
3. "I find it rather amusing that the TC calculator gave me all kinds of tuning formulas to follow. (snip) It has not been my experience that the primary tuning has been anywhere close to accurate for me." What "TC calculator" are you using that is giving you such inaccurate results? Modern, sophisticated applications such as JAVATC are EXTREMELY accurate, if the input data is accurate. If your inputs are inaccurate, then how can you expect valid outputs? Garbage in = garbage out. In 100% of these cases where I have aided someone in debugging their coil, and they complained about the design software not giving valid outputs, the root cause was inaccurate input parameters.
You might want to visit Richie Burnett's extremely informative Tesla coil website to get a better understanding of how Tesla coils work, and the formulas that can be used to develop the parameters that are important to achieving resonance.
Registered Member #1535
Joined: Wed Jun 11 2008, 11:37PM
Location: Northeastern Pennsylvania - USA
Posts: 117
3.5 x 20 yields an aspect well over 5 to 1. I've achieved much better results by staying around a 4 to 1 ratio with a power supply that size. Shorter fatter coils work better for me.
How about around a 20" wind of 23awg wire on a 4.5" form. This is close to the same inductance. Do the actual math to get the best wind length.
When I went from a 3.5"x16" to a 4.5"x16", I gained several inches of open air arc length.
Registered Member #1127
Joined: Mon Nov 19 2007, 12:08AM
Location:
Posts: 139
Herr Zapp wrote ...
MOT Man -
Sorry, but your statement that "You need at least 15 turns to get a coil up to resonance with 1/4" tubing" is, well, completely ludicrous.
A Tesla coil can be designed (and operated) with a 1-turn primary, or with a 30-turn primary. The critical factor is that the primary and secondary circuits have the same resonant frequency during operation.
You are also confused about a few other issues:
1. "More turns mean higher resonant frequency, usually." This is 100% wrong. Simply adding more turns to either a primary or secondary coil will always DECREASE the resonant frequency, period. There is no "usually" involved. If you throw a rock vertically up into the air, it will always come back down, period.
2. "A secondary wound with a higher AWG number means that automatically you will have a higher resonant frequency ~ generally". This is 100% wrong. The "higher" (larger) the AWG number is, the smaller the wire diameter, and the larger the number of turns per a given unit of secondary coil length. The larger the number of turns, the LOWER the resonant frequency, period. Again, there is no mysterious "generally" factor involved.
3. "I find it rather amusing that the TC calculator gave me all kinds of tuning formulas to follow. (snip) It has not been my experience that the primary tuning has been anywhere close to accurate for me." What "TC calculator" are you using that is giving you such inaccurate results? Modern, sophisticated applications such as JAVATC are EXTREMELY accurate, if the input data is accurate. If your inputs are inaccurate, then how can you expect valid outputs? Garbage in = garbage out. In 100% of these cases where I have aided someone in debugging their coil, and they complained about the design software not giving valid outputs, the root cause was inaccurate input parameters.
You might want to visit Richie Burnett's extremely informative Tesla coil website to get a better understanding of how Tesla coils work, and the formulas that can be used to develop the parameters that are important to achieving resonance.
See:
Regards, Herr Zapp
Well I am making a statement in regards to the coil parameters presented here - I should have made that clear. I didn't. My mistake. I measured my 4" secondary and it measures 253 kHZ wound with 27 AWG. I measured my 8.25" secondary and it resonates at 113.287 KHz ~ JAVA TC puts the frequency at 112.79 it is wound with 23 AWG. Which coil has a higher resonate frequency.
Primary - I'm talking about adding extra turns for a broader range of frequency. I've found that the primary tap tends to be off considerably during tuning - even when my power supply has been metered correctly. So I currently have a 6" TC that should have been tapped at turn 6 for best output. But it works best when tapped at turn 8. Capacitance and power levels remain constant. In 10 years ~ I've gone by my numbers and things have worked pretty well thus far. No need to jump all over what I said - just stating that I've found some oddities with the formulas presented on JAVATC. That doesn't mean I haven't made mistakes too. I think that is a part of coiling. I've just seen some interesting results with my coils after the capacitance and power inputs have been set.
The larger the number of turns on the primary = lower resonant frequency.
Registered Member #1799
Joined: Thu Nov 06 2008, 02:20AM
Location:
Posts: 23
Herr Zapp wrote ...
Nick -
I agree that you should be able to achieve better than 20" output from your system, but optimizing a coil's performance frequently takes a lot of experimentation and incremental changes. First, a few questions about your coil:
1. Is your "20 inch" output the free air (streamer) discharge length, or discharge length to a grounded target? 2. Are you absolutely sure that BOTH legs of BOTH NSTs are developing full output? How did you verify this? 3. Are the outputs of your NSTs properly phased? How did you verify proper phasing? 4. Please describe your tank capacitor: MMC or something else? Construction, dielectric material, etc. How did you determine the exact ".0137uF" value? 5. What gage wire is used to connect your spark gap, tank cap, and primary coil? 6. Please describe your 8-segment spark gap: design, electrode material, electrode shape, etc 7. What are you using as a secondary ground? 8. How is your 4" X 14.7" toroid constructed? What material is it made from?
Is there any way you can post some detailed photos of the coil's construction? Frequently, this gives the best insight into design or construction problems.
Regards, Herr Zapp
1. Ground strike from break-out point to grounded rod. 2. No. Verification as follows:"both of these start arcing at the same distance (isolated from tank circuit)" Also, one was GFI but the GFI magically stopped interferring (it was pulsing before). I guess I should make some kind of voltage divider to test the stupid things. However, the gap does seem to fire pretty quickly. Maybe I can do some kind of audio analysis to determine the break rate? 3. "hmm, this way makes spark, this way does not." 4. 14"x14" squares of 6mil ldpe (15 between each 10"x12" plate). Chinese ebay LCR meter, but i think capicitance isn't too hard to measure and it "says" it's rated for 5% accuracy. Max spark length is achieved when close to what JavaTC says for number of p turns. 5. 1/4" copper tubing and "Aluma-Rope". I made what I think to be a good high frequency conductor. For the length of the rope I unroll just a little bit more length in aluminum, then roll the foil around the rope. 6. .42" acrylic and 3" segments of .875" OD copper (3/4" pipe). I drilled holes in the acrylic, and used bolts to hold the pipe sections together. The outside pipe sections have 1/4" copper tube soldered to them. The gap isn't the problem. (I have a vacuum thing setup too). 7. 3/4" copper pipe. hammered in the ground. 8. The "semi-rigid" aluminum pipe stuff that bends (4.35" OD) then a 6" thin wood disc is hotglued in the middle. Covered in foil tape.
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15kV 30ma x2, 13.7nF, 8 series static gap, 20" max spark length.....?
