Chris raises an interesting point here. This is much like a catch-22 analogy.
A lower inductance would mean faster charging of the magnetic field, however, max output potential favors a higher inductance and large dia sec coilform.
Also, the IGBTs used in solid state coils like to switch at or below 50 kHz which usually again requires larger inductance and either large dia coilform or lots of sec turns. Too many turns and you begin to run into the tradeoff points between getting large inductance vs. too much resistance.
Some experimenters use as many as 2,600 turns on the sec to keep the switching freq low while other experimenters prefer to use large dia sec coilforms. With solid state coil designs, I prefer around 1,800 sec turns and the largest dia. sec coilform possible. The balance here, of course, it the size of the sec toroid which increases with large dia sec coilforms --- and the cost rises with the larger toroid sizes.
I use k value of 0.17 to 0.18 for most designs. You can do a lot of "what-ifs" in JAVATC to check the coupling values for different inner and outer pri coil radii.
Certainly a lot of trade-offs to consider for optimum performance at reasonable cost.
Bart Anderson's JAVATC program enables experimenters to try many different configurations to achieve desired performance, and then a cost analysis is conducted for each different configuration.
My personal preference is to "best guesstimate" the cap size and then use the "auto-tune" feature in JAVATC to determine best pri number of turns to match. In most solid state coils values between 0.6 uF and 1.5 uF are common with pri sizes of around 4 turns. You can use less but then tuning points on the primary become very critical. Use 4-5 turns with a 0.6 to 1.5 uF pri cap and see what JAVATC tells you to use for the primary. I like around 1.0 to 1.5 uF with 3.5 to 4.5 turns on the pri tap. Then, I check the calculated JAVATC coeff. of coupling (k value) to see if it is in the 0.17 to 0.18 range. I make inner and outer radii adjustments as necessary to get the k value in this critical range. The idea is to couple as tight as possible but definitely to not "overcouple" and get into the "racing sparks" range --- usually a value of 0.2 or above.
16 inch dia. sec coilform with 34 x 8.5 toroid atop a 24 x 6 inch toroid. These can be spun toroids or, if cost is a major consideration, the good old aluminum tape dryer duct type toroids work fine. Sonotubes coilforms or fiberglass work equally well.
BTW, if anyone is working on a solid state design I have developed some "datasheets" that can be helpful to setup of over design and also a separate datasheet for pri-sec geometry. Filling in these sheets first with dimensions helps transfer the data into JAVATC for the test runs. Contact me off-list if you want them emailed to you. Also, if anyone needs help with JAVATC initial run contact me off-list for assistance.
Many happy sparks, Dr. Resonance Resonance Research Corp. www.resonanceresearch.com----- Original Message ----- From: <FutureT@xxxxxxx>
To: <tesla@xxxxxxxxxx> Sent: Thursday, November 22, 2007 11:39 AM Subject: Re: [TCML] quench times again
In a message dated 11/22/2007 11:47:26 A.M. US Eastern Standard Time, list@xxxxxxxxxxxxxxxxxxxxxxxxx writes:I am also trying to work out, that other than coupling and frequency whicheffect the tank "transfer speed" to secondary... can the secondary itself become "easier to drive" to make the transfer quicker ? this is why I thought that a lower inductance would take less time to "charge" and the energy transfer would be quicker than a lower inductance.... though this could just be down to a higher frequency...cheers, ChrisChris, I'll ignore the arc-to-ground case which is a special case. Mostfolks like to see mostly air streamers I think. The transfer speed to thesecondary is not the problem preventing fast quenching. The real problem is streamer (actually leader) impedance. If the streamers were somehowof a lower impedance, this would drain the energy faster from the secondary.Low impedance results in a heavier loading effect by the streamers. If the streamers were of low enough impedance, then there would be noenergy left to go back into the primary and prevent quenching. The effectof streamer loading reflects back through the system to affect the quench time. In the case of the arc-to-ground, the streamer impedance becomes very low, and drains the energy quickly. If the energy transfers to the secondary quickly, but can't get out quickly via the streamers, then there's a bottle-neck, a traffic jam. It's as if many cars are streaming onto a highway from various feeder roads, but up ahead a couple of lanes are shut down for repair. Now the traffic backs up. If the cars speed quickly to that bottle-neck, it won't do them a lick of good. They'll still have to slow down or stop until the traffic ahead makes its way through the constriction. Souping up the engines of the cars, or reducing the friction of the car's powertrain, etc. won't help. The only thing that will help is to remove the constriction, to open the lanes of the highway which are closed for repair. This opening of the lanes, would be analogous to reducing the impedance of the streamers of the TC. John**************************************Check out AOL's list of 2007's hottestproducts. (http://money.aol.com/special/hot-products-2007?NCID=aoltop00030000000001) _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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