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Voltage/Length (fwd)(the Kevlar thread)
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From: Jim Monte [SMTP:JDM95003-at-UCONNVM.UCONN.EDU]
Sent: Wednesday, February 11, 1998 12:44 PM
To: tesla-at-pupman-dot-com
Subject: Re: Voltage/Length (fwd)(the Kevlar thread)
>From: John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
>Sent: Tuesday, February 10, 1998 12:50 AM
>To: Tesla List
>Subject: Re: Voltage/Length (fwd) (the Kevlar thread)
>
>
> Greg, Jim, All -
>
> There are two problems with what is shown below.
> The 985 KV (Vs) cannot be measured with any instruments to verify this
>voltage.
I thought the point of this was that the 985kV secondary voltage was
a reasonably accurate voltage estimate that needed to be explained/
correlated with other system parameters.
> The 24.2 J assumes RMS conditions which do not exist in the Tesla coil
>secondary circuit.
What are "RMS conditions"?? I've heard of steady-state conditions,
transient conditions, and boundary conditions, but never "RMS
conditions". I have only heard RMS (Root Mean Square) being used to
quantify the average value of a voltage or current. For a periodic
voltage v(t) with period T, the RMS voltage = sqrt(IT(v(t)*v(t))/T),
where IT(x) is the integral of x over 1 period.
>
> Note that watts = joules/dt = volts x amps x cos A
watts = joules/dt is not accurate. You are dividing energy by a
differential quantity dt. AVERAGE watts for a time interval from
time t1 to time t2 = (joules removed from the system in this interval)/
(t2-t1). INSTANTANEOUS watts for any instant of time t = d(joules)/dt.
watts = volts x amps x cos A is an AVERAGE amount of watts for
SINUSOIDAL voltage and current when "volts" and "amps" are the RMS
values and "cos A" is the phase angle. Even if "volts" and "amps"
are RMS values, this expression will not work for a non-sinusoidal
waveform, in general. (Try it with a square wave!)
> What did you use for "dt" and "cos A" to satisfy the non RMS conditions?
I can't answer this without knowing what you mean by "RMS conditions".
I can however say that the calculations below are based on all
secondary energy (at one instant of time) being stored in the toroid
cap, which is treated as a lumped C. This is overly optimistic, but
it is a lower bound on the secondary energy for a given Vs (excluding
the improbable case of harmonics playing such a great role in
secondary that even the toroid cannot be considered to be a lumped C).
>
> The Vs voltage can be estimated by using the spark length and comparing it
>with the tests results of high voltage labs.
Didn't you agree earlier that spark length is a function of the break
rate as well as Vs? If this is true, you can't estimate Vs using only
the spark length. Doing so would be analogous to estimating the voltage
across a resistor from the current passing through it, without taking
into account the R value of the resistor!
Regarding your post about various ways to find secondary voltages, I
think that if these give different values, that supports the belief
that the secondary cannot be treated as a lumped circuit. Otherwise
the results would agree.
Another minor comment that isn't worth its own post is that, to
further muddy the issue regarding parallel and series connection of
the toroid and Cself of the coil, there is also an issue of partial
capacitance with the various windings of the coil.
Jim Monte
>
> John Couture
>
>-----------------------------------------------
>At 08:59 PM 2/8/98 -0600, you wrote:
>>
>>----------
>>From: Greg Leyh [SMTP:lod-at-pacbell-dot-net]
>>Sent: Saturday, February 07, 1998 11:47 AM
>>To: Tesla List
>>Subject: Re: Voltage/Length (fwd) (the Kevlar thread)
>>
>>Jim Monte wrote:
>>> <snip>
>>> You may be able to argue that even the toroid is large relative to the
>>> wavelengths of some harmonics, but assume we store all the energy
>>> in the topload cap. Redoing with a primary cap of 100nF and only the 50pF
>>> toroid cap in the secondary,
>>> Primary Energy = 0.5Cp x Vp^2 = 33.8J (at 26kV)
>>> Secondary Energy = 0.5Ctor x Vs^2 = 24.2J (at 985kV)