Re: Fw: Primary RMS Current calculation

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

On 28 Feb 01, at 8:01, Tesla list wrote:

> 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.

What about the duty cycle? The circuit is pretty quiet in general for 
90% or more of the time in between gap fires.

Malcolmk