[Prev][Next][Index][Thread]
Re: Toroid Question (fwd)
Subject: Re: Toroid Question (fwd)
Date: Fri, 2 May 1997 18:53:30 +1200
From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization: Wellington Polytechnic, NZ
To: tesla-at-pupman-dot-com
Hi Alfred, all,
I wrote a program to calculate the optimum former h/d
ratio for a given length of wire. Method: start with a length of wire
and h/d = 50, then increase d as l is decreased. The answer the
program gave me was just under 0.5. Not great for coiling except with
a gigantic coil because of the height. Not the same as maximum Q
(without terminal) either. That turned out to be h/d=1, confirmed by
measurement.
Malcolm
<snip>
> BTW the coil you are working on is not exactly the best design, the
> Length/Diameter ratio is too high! This coil has an L/D ratio of 6,
> you shouldn't use anything larger than 4 and preferably it should be
> around 3. If you look at all of Dr. Tesla's coils they are barrel
> shaped this is in part due to the fact that the input to output ratio
> of a Tesla Coil is determined by;
>
> Voutput = Vprimary X SQRT(Lsecondary/Lprimary)
>
> consequently we want as large an inductance in the secondary as
> possible and it turns out that the optimum L/D ratio for maximum
> inductance for any given length of wire is roughly 3. The primary you
> stipulated of 12 turns is also a bit high, referring to the input to
> output ratio given above it can be seen that the maximum output will
> require as small an inductance as possible on the primary. I have
> found it best to keep the number of primary turns to 6 or less, a
> Tesla coil really dose'nt need much of a primary only enough to
> transfer the primary circuits energy to the secondary and at
> frequencies of 100 Khz and above you don't need much more than a turn
> or so. I couldn't say if your primary capacitance is right or not
> without knowing the current rating of your transformer to calculate
> it's output impedance.