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Re: [TCML] Photos of my coil.

Thanks David,

Apparently I'm learning the hard way that NST's are pretty fickle :P. I have
also consildered adding vanes to the rotor just to move some air through the
gaps for quenching. I was wondering though just how to calculate NST
impedance, and how that relates to resonance in the tank circuit such that a
safe capacitor voltage can be found. Do I need to move closer to, or further
away from .005 microfarrads?

I'll contact you about the variac!



On Sun, Aug 9, 2009 at 7:42 AM, David Rieben <drieben@xxxxxxxxxxx> wrote:

> Hi Austin,
> Very nice looking Tesla coil project.
> You're gonna find (at least I did) that NSTs are no-
> toriously fragile in Tesla coil service. The Terry filter
> will probably help with this but one of the main issues
> that causes NST failure in TC duty is the opening of
> the SG too wide, which allows the the resonant volt-
> age created between the NST's HV secondary
> winding and the primary capaitor to "go theough the
> roof". However, since you have a synchronous ro-
> tary gap, this should not really be an issue for you,
> assuming that you have it synched correctly.
> Also, your primary cap should be at least 2X reso-
> nant for the mains frequency and your transformer's
> rating. Since a 15/30 NST at 60 Hz is going to be
> resonant at around .005 uFd, you are right near the
> "border" with you .093 uFd. primary cap. But, as
> I was saying earlier, I have personally found that
> NSTs tned to be very fragile when used for this
> purpose irregardless of whatever precautions that
> I take and I also realize that powering a Tesla coil
> is pretty much way out of the designer's intended
> purpose for this type of transformer.
> I may also have an extra variac that I could let go
> of that would work for you. Contact me off list
> for more details and check out my Flickr page
> of my coil project:
> http://www.flickr.com/photos/33464569@N05/
> David
> ----- Original Message ----- From: "austin feathers" <kartkid1@xxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Sunday, August 09, 2009 12:37 AM
> Subject: [TCML] Photos of my coil.
>   Hey all! It's Austin. Heres my flikr account, along with photos of the
>> coil
>> I'm constructing. I'm an aspiring coiler and would very much welcome any
>> critical observations or queries as to the design and how it may be
>> improved.
>> http://www.flickr.com/photos/thedangerousnerd/sets/72157621985544942/
>> Also, I've been pondering the death of my first 15Kv 30 milliamp
>> Franceformer neon sign transformer. I'll admit that I didnt have the terry
>> filter grounded, but the autopsy (trying to draw an arc from either pole)
>> revealed that either the primary was done for, or that both secondary
>> windings failed, in that if one of the secondary coils were intact, I
>> should
>> (?) be able to get 7,500v from a surviving pole to the transformer case.
>> Any idea what happened, or what I might do to protect a new transformer?
>> Thanks!
>> Austin
>> P.S. I'm looking to procure anywhere from a 10-25 amp variac for main
>> voltage controll, as well as a 15Kv 60milliamp NST. Should I just throw
>> money at it? Or do you guys have some kindof high-voltage fairy that stops
>> by with loads of surplus components...
>> _______________________________________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxxxxxx
>> http://www.pupman.com/mailman/listinfo/tesla
> _______________________________________________
> Tesla mailing list
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