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I am so wondering HOW you guys manage to get a low peak current on the primary given on that output length of about 6 ft? my coil shoots a meter but having a 120+ Amps on the primary, i doubt that even when my Ipk reach 160 it will produce the same result as yours. I've researched some russian QCW coils, and as expected, they need about 250-300 Amps to reach 6" sparks. So what's your Magic steve? :)
May we know that coil's coupling? Is it phase shifted shared bridge or DC modulated supply? what's your Bridge's Voltage in?
I think the kind of tuning helps a lot here, i.e. the one Steve conner proposed to tune the primary lower and run at the upper pole frequency. As the spark drops the secondary resonant frequency, the coil becomes more and more in tune allowing the inverter to pump more power into the spark. This requires a different drive design though. The tesla gun uses the phase shifted method. It seems that BSVi's phase shifted coil does the same kind of tuning and has also achieved really long sparks (2m!) with not so much current.
Registered Member #3964
Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332
loneoceans wrote ...
I think the kind of tuning helps a lot here, i.e. the one Steve conner proposed to tune the primary lower and run at the upper pole frequency. As the spark drops the secondary resonant frequency, the coil becomes more and more in tune allowing the inverter to pump more power into the spark. This requires a different drive design though. The tesla gun uses the phase shifted method. It seems that BSVi's phase shifted coil does the same kind of tuning and has also achieved really long sparks (2m!) with not so much current.
thanks loneoceans, hmmm.. these QCWs are getting more interesting than before, now that "finally" someone spoke up really helpful :)
so are you saying that in steve's video he uses Phase shifted topology and not the converter approach to get his primary current down? also, have you seen this vid?
this is a work of Barmaley (maybe he's a russian too) - i found that he's using a buck converter supply (sync buck) but he's just using a iron core for the Inductor Output of the Buck (Strange!) -this is a huge size iron cored inductor :) but as you can see, his works can be compared to other top QCW record holders :) this too works with smaller currents too..
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
Julian I would think that iron would be a logical choice since the smps ramp is in the 20 ms range since iron has a response up to 400 hz. I have read in places like
and hear
that the L and C filter works by storing energy. I see that it pausible that the tesla converts this stored energy as it ramping up. A good choice would be to make your inductor with metglass because it has the highest permeability with a frequency response of 100kHz.
Registered Member #3964
Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332
teravolt wrote ...
Julian I would think that iron would be a logical choice since the smps ramp is in the 20 ms range since iron has a response up to 400 hz. I have read in places like
and hear
that the L and C filter works by storing energy. I see that it pausible that the tesla converts this stored energy as it ramping up. A good choice would be to make your inductor with metglass because it has the highest permeability with a frequency response of 100kHz.
Thanks for these information. Maybe we were just relying too much on the early/pioneer researchers, that only Ferrite Core would be the best and that suits for buck converters. Actually, I don't have that experience with regards to these core materials in SMPS topologies.
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
For the buck converter you need a powdered iron core, or MPP (Moly-Permalloy Powder, like deluxe powdered iron) or a ferrite core with an air gap. Ungapped ferrite is no good, and I doubt Metglass would be any good either. These are high permeability materials for transformers, they saturate too easily for an inductor that needs to store energy.
A laminated iron core with an air gap might well work, at least in Soviet Russia.
I am so wondering HOW you guys manage to get a low peak current on the primary given on that output length of about 6 ft?
There are a number of factors which influence primary current: a) Primary impedance. A larger impedance decreases primary I. You seem to have a large primary Z, so I don't think that's your particular problem. b) Coupling, a higher coupling will also decrease current. Your coupling is also large (0.4?), so that's also not an issue. c) Tuning, don't know waht your primary and secondary fres are, so it's hard to tell. But I guess you have played around with that. d) Secondary Z. There is a sweet spot for secondary inductance. Both too low or too high will lead to a large primary I. Check for secondary inductances of other successful builds.
Wrt to arc length: a) Power, loneoceans coil currently has 150V and 120A (full bridge) input. Peak power is then 150*120*2*2/pi = 23kW. That's pretty much needed for 1m arcs. b) Straight arcs, made with the right rampup are longer than short burst arcs. So the right current envelope will also increase length.
To diagnose the problem it would help to know primary and secondary tank parameters and a scope shot of primary current and secondary voltage (picked up with an antenna).
Registered Member #3964
Joined: Thu Jun 23 2011, 03:23AM
Location: Valenzuela City
Posts: 332
Uspring wrote ...
I am so wondering HOW you guys manage to get a low peak current on the primary given on that output length of about 6 ft?
There are a number of factors which influence primary current: a) Primary impedance. A larger impedance decreases primary I. You seem to have a large primary Z, so I don't think that's your particular problem. b) Coupling, a higher coupling will also decrease current. Your coupling is also large (0.4?), so that's also not an issue. c) Tuning, don't know waht your primary and secondary fres are, so it's hard to tell. But I guess you have played around with that. d) Secondary Z. There is a sweet spot for secondary inductance. Both too low or too high will lead to a large primary I. Check for secondary inductances of other successful builds.
Wrt to arc length: a) Power, loneoceans coil currently has 150V and 120A (full bridge) input. Peak power is then 150*120*2*2/pi = 23kW. That's pretty much needed for 1m arcs. b) Straight arcs, made with the right rampup are longer than short burst arcs. So the right current envelope will also increase length.
To diagnose the problem it would help to know primary and secondary tank parameters and a scope shot of primary current and secondary voltage (picked up with an antenna).
Hi upspring, thank you very much for your comments, by the way, here are my coil's specifications and output from JAVATC. I don't know too if the Impedance/Inductance of my Secondary is not in "good shape" to get swordish sparks.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Uspring wrote ...
Wrt to arc length: a) Power, loneoceans coil currently has 150V and 120A (full bridge) input. Peak power is then 150*120*2*2/pi = 23kW. That's pretty much needed for 1m arcs.
I think its just Vout*Ipk*2/pi, so 11.5 kW in this case.
zzz_julian_zzz: Your secondary specs look reasonable. It'd be nice to compare them to loneoceans, but I couldn't find them in his writeup. What does your primary current rampup look like?
Dr. Dark Current:
I think its just Vout*Ipk*2/pi, so 11.5 kW in this case.
I was under the impression, that he switches between +150 and -150V with a full bridge, i.e. an effective input voltage of 300V. (?)
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Small QCW
