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Re: Fired, but need help
Patti,
I agree with the others. Over-coupling is the most likely cause of secondary
arcs. I have observed this as arcs traveling down the secondary. When I was
having the same problem, the arcs would travel down the secondary and then arc
out to my strike rail. I did a series of adjustments to stop it. Raising the
secondary does help in this situation. However, I did add 3 coats of spar
varnish to the secondary windings and this too made a difference (occurrances
decreased substantially). I then went through a series of tuning adjustments
using an rf ground rod to tune by. Since that time, I didn't have an arc to
the
secondary until I started turning up the juice. During an outside "very cool"
run, I noticed I had arced to the secondary and burned a winding (about 1/4 up
from the bottom). I didn't see this happen, but the inspection following
the run
revealed it (always inspect after a run!). It was easily repaired. These
situations were all with a flat primary. It is possible to overcouple with a
flat primary, but as others have stated, it is more unlikely to happen
compared
to a helical or anything in between.
Bart
Tesla List wrote:
> Original Poster: "Patti" <asrai-at-palmnet-dot-net>
>
> Hello Listers,
>
> This weekend the weather held out so I was finally able to achieve first
> light. Results after safety gap, RSG, secondary height and toroid
> adjustments was 68" to a ground rod suspended on a ladder. I did have a
> number of strike rail hits, so I raised the toroid up to a height of 18"
> above the top of the secondary. My final voltage was about 196 VAC at 22
> amps to the 10KVA 14.4kv pole transformer that is current limited by a
> variable inductor with a range of .68 MH to 8.9 MH (setting was 6.9) and 2.9
> ohms of 10kw heater elements in series.
>
> One problem though, and I need some help.
>
> I'm getting numerous strikes along the outside of the secondary, starting
> with the top winding to the bottom winding. Also I suffered some damage two
> turns about 5 inches up from the bottom of the secondary. It got a bit
> cooked. Right now I have the secondary bottom winding sitting about 1.25
> inches above the primary. I'm running safety gaps at the caps at 1/2 inch
> and 5/16 inch on each side of the ground post tied to RF ground for the pole
> transformer. The specs are:
>
> Capacitor: 2 .22mf 50KVDC csi caps in a series for .11mf total
>
> Toroid: 48" x 12" Aluminum duct wrapped with aluminum tape 53 pf
>
> Primary: 100ft of 1/2 diam. copper tubing starting at 7.3125 inch radius
> and ending with 19.8125 on turn #15. Spacing between turns is .250 inches.
> Lpri needed for cap and toroid 50.8uh. Currently tapped at about 8.5 turns.
>
> Secondary: 1000 turns of 22 AWG magnet wire wound on a 10.5 inch PVC duct
> that was coated with .125 inches of polyurethane before winding for a total
> winding length of 32 inches. wire measures .032 in diam. Coated with 1/16"
> of polyurethane.
>
> C=16.5 pf Lsec+ 80.5 mh
>
> Resonance frequency of secondary with toroid installed: 67.3 Khz Without
> toroid: 138.3 Khz
>
> H/D ratio: 3.0 to 1
>
> Used Medhurst constant of .61
>
> I've worked the calculations using the formulas from the archives, other
> list memeber's web pages and Wintesla program to make sure I'm getting
> approximatly the same results. Any help would be appreciated especially on
> fixing secondaries and how to stop the cookage.
>
> Patti