Fw: Primary RMS Current calculation

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Original poster: "Charles Hobson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <charles.a.hobson-at-btinternet-dot-com>


----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, February 28, 2001 2:22 AM
Subject: Primary RMS Current calculation


> Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>
>
> Hi All,
>
>         I have received a number of inquiries about primary circuit RMS
> current and using MMCCalc for different types of capacitors.  MMCCalc
displays
> the current:
>
> http://hot-streamer-dot-com/TeslaCoils/programs/Mmccalc2.zip
>
> The RMS current is calculated using the formulas in MMCPower4.html.  The
> equations for resistance of a single cap (Rcap) and power dissipated in a
> single cap (Wo) can be used to find current by simply using Ohm's law.
>
> P = I^2 x R  ==>  I = SQRT(P / R)
>
> So the RMS current in a single cap (which is the same for a single string)
> is:
>
> Irms = SQRT (Wo / Rcap)
>
> The Primary RMS current is simply that number multiplied by the number of
> strings
>
> Iprms = SQRT (Wo / Rcap) x Nstring
>
> MMCPower4 is at:
>
> http://hot-streamer-dot-com/TeslaCoils/MMCInfo/MMCPower4.html
>
> Cheers,
>
>         Terry Fritz
>
Hello all,

I have been thinking about another method for calculating rms current in the
primary circuit (MMC and primary coil). Not being certain of its validity, I
would appreciate  comments.

 Knowing the MMC value and the voltage it charges up to before spark gap
firing, I would first calculate the energy in the MMC. Joules = 0.5V^2C to
get a feel for what's going on.

This energy moves back and forth between the MMC and the primary coil during
oscillation.Since energy in a coil  is Joules = 0.5I^2L

then    0.5V^2C  =  0.5I^2L  or I = V(C/L)^0.5  (peak current at the instant
all energy is in the coil).

I rms = peak I x 0.707.

Of course getting two bursts of RF during each ac cycle (120/s in U.
S.),each burst lasting several cycles of RF (if perfect quenching is
achieved), and some loss of energy due to circuit resistance then the
current over  one  second becomes problematical. So back to square one on
rms, average etc. current in this area. .

I would think that what the MMC has to put up with in terms of peak RF
current and voltage stresses are of major concern since both are usually
very large.

Again please, if there are flaws in my reasoning, I would be most anxious to
know about it.

Regards  Chuck.