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RE: Voltage determination
Malcolm, David, All -
It should be understood that the output spark length shown by the JHCTES Ver
3.1 computer program is only a ball park figure. As I said in one of my
previous posts "there are many other design considerations". The spsrk
length is dependent upon many conditions. It's just about imposible for a
program to be able to allow for all of the variables. The spark length is in
the JHCTES program because several coilers asked that this be done. However,
don't take the spark length too seriously.
With the JHCTES program there are coil designs where changing only one input
will change the spark length. The computer changes all the other variables
to keep the system in tune. Sometimes changing more than one input will be
required to obtain a correct spark length output. That is generally when
changing one input changes the energy input to the TC system. You then have
to change the input current of the power transformer. The computer will
again change all the other parameters to keep the system in tune. The spark
length will also change when the power transformer secondary voltage is
changed (Tesla coil primary voltage).
Someday another coiler will produce a TC program that includes the spark
length. It will be interesting to compare this program with the JHCTES.
John Couture
------------------------------
-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, July 25, 2000 7:52 PM
To: tesla-at-pupman-dot-com
Subject: RE: Voltage determination
Original poster: "Malcolm Watts" <M.J.Watts-at-massey.ac.nz>
Hi John,
On 25 Jul 00, at 18:49, Tesla list wrote:
> Original poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>
>
> Bart -
>
> It is a well known fact that the secondary coil inductance affects the
> length of the output spark. This is the main reason that 1000 turns are
used
> instead of 100 turns for a Tesla coil. The 1000 turns gives more
inductance
> and longer sparks. Of course there are many other design considerations.
The
> theoretical equation is
> Vs = Vp sqrt(Ls/Lp)
> Note that when Ls is increased the secondary voltage Vs is increased which
> in turn increases the spark length. The factor I used is non linear and
> obtained from empirical data and using mathematical regression.
In order to increase Ls you *have* to change something else if
tune is to be maintained, whether it is decreasing Cs
(physically smaller coil, hence smaller wire, hence higher
secondary losses), increasing Cp (in which case you'd have to
lower Vp in order to retain an identical Ep = same Vout) or
increasing Lp (in which case the impedance ratio is the same =
same Vout). I think it is unrealistic to simply attribute
increased sparklength to a change in one variable only when in
reality others change or must be changed as well. The
foregoing arguments assume negligible losses in the primary
which isn't true either and then of course any modification to
either coil affects k. Not so simple I would say.
Regards,
malcolm
> Empirical Tesla coil design is a complex combination of many parameters
> involving both theoretical and empirical equations. The Tesla coil output
> spark length equation is obtained from empirical data and subject to many
> variations.
>
> John Couture
>
> --------------------------------
>
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Tuesday, July 25, 2000 11:13 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: Voltage determination
>
>
> Original poster: "Barton B. Anderson" <tesla123-at-pacbell-dot-net>
>
> Hi John,
>
> Couple questions below:
>
> Tesla list wrote:
> >
> > Original poster: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
> >
> > How about using the following equation that takes in the most important
> > conditions that affect the output spark? One advantage of using factors
is
> > that you do not need to know the efficiencies. The factors are based on
> > empirical data.
> >
> > Spark length = W*Vp*Ls*B
> >
> > W = Input watts
> >
> > Vp = Factor for Tesla primary volts
> >
> > Ls = Factor for secondary inductance
> >
> > B = Factor for breaks per second
> >
> > The JHCTES program uses a similar equation.
>
>
>
> How is the secondary's inductance important to spark length? I can see
it's
> importance to Fr, but not to spark length (power processing maybe?).
> Inductance
> is a factor that naturally increases with coil size - size generally means
> more
> power applied and therefore greater spark length. Is it possible that
> inductance here is mistaken as a factor due to naturally occuring
mechanics?
> Maybe not, I just haven't seen a reason Ls would be thought of as a major
> factor to spark length, and if it is, I'd like to know why?
>
> The equation would suggest just increasing Ls to gain spark length. I'm
sure
> you didn't mean the equation in that way. Maybe you are referring to a
> higher Q
> secondary?
>
> Thanks,
> Bart
>
>
>
>
>