[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [TCML] Turn-to-Turn short circuit



Sorry I didn't get back to you sooner, but I was out doing field work today.
My transformer is a NST, at 8kv, and 30mA. Yeah, 5MVsounded a *little *high.
200kv is a little more manageable. This is just a small coil for a science
fair, so I don't need it to big. Thanks for the equations, (and the reality
check). They will come in handy. I think I had the formulas somewhere, but
this will save me from having to look for them.
Also, (for Mr. Karr) I have access to some 26AWG wire, would this maybe be a
little better?
I guess I don't know as much about this stuff as I would like to think! ; )

Matthew


On Fri, Mar 20, 2009 at 4:17 PM, bartb <bartb@xxxxxxxxxxxxxxxx> wrote:

> Hi Mathew,
>
> The reason I'm asking about supply transformer is to help you avoid
> frustration and mistakes: For example, disregarding various issues about
> losses, with your dimensions on the secondary and assuming a small toroid
> (say 2" x 10"), the coil would resonate at 138kHz and would require a .06uF
> cap size for 10 primary turns to attain resonance (which is key and
> fundamental). In order to provide an adequate charge cycle (ability of power
> supply to charge the tank cap), the power supply transformer would need to
> be nearly 3KVA (example is maybe a 12kV at 250mA output).
>
> There are many problems with your secondary (h/d ratio, high losses, other
> downstream needs) and there is the fact that 5MV coils only exist in the
> most extreme "Golka" size coils). Our hobby coils are in the 200 to 500 kV
> range. That's the reality. This can be quite a dramatic psychological effect
> on your brain once you realize the details.
>
> The voltage at the output terminal is better described as Vtop = Vpri x
> sqrt(Lp/Ls), where Vpri is your peak output supply voltage and Lp and Ls are
> the primary and secondary inductances.
> Vpri = 12,000 x 1.414 = 16968V.
> Lp = 21.71uH
> Ls = (90.9mH at resonance)
>
> Vtop = 16968 x sqrt(21.71uH/90.9mH) = 262kV.
>
> Even this is an ideal transformer model. In a practical application, maybe
> 70%, so 183kV. Nothing near 5 million volts. This is what you can expect
> from your particular secondary. It should be higher for a well designed
> sparking Tesla Coil, and about 2x as high. Your secondary geometry is what
> should be looked at. The power supply is a good place to start developing
> the secondary, and why I ask if you already have a transformer.
>
> Take care,
> Bart
>
> bartb wrote:
>
>> Hi Mathew,
>>
>> Your likely going to get a few replies on the statements below for a many
>> reasons, but I'm curious, do you already have a transformer you plan to use?
>> If so, what are is the output voltage and output current ratings?
>>
>> Bart
>>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla