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Re: FW: Re: Tesla Coil Efficiency Test
Original poster: "D.C. Cox by way of Terry Fritz <twftesla-at-qwest-dot-net>" <DR.RESONANCE-at-next-wave-dot-net>
Most large coils running around 1 MEV can be safely loaded to around 50 mA
continuous without potential degradation. Around 75 mA the potential begins
to drop off considerably. I'm talking a 18-20 inch dia. secondary.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
Sent: Monday, June 17, 2002 3:58 PM
Subject: Re: FW: Re: Tesla Coil Efficiency Test
> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
> Tesla list wrote:
> > Original poster: "John H. Couture by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
> > I agree that this test loads the secondary and reduces the output
> > However, don't we want to have a secondary load so the useful output is
> > zero?
> But a resistive load in a normal Tesla coil only appears after breakout,
> not all the time.
> > For the TC efficiency shouldn't this be the integrated and RMS
> > output/input, otherwise, the efficiency would be an instantaneous or
> > type?
> The figures would be almost identical. There is no activity in the
> secondary while the primary gap is open, and so in the interval
> between firings there is energy loss only in the charging of the
> primary capacitor. To take this into account, a conventional wattmeter
> at the input side of the system, including power transformer, variac,
> etc., would produce an accurate reading of the average input power,
> and then the efficiency would then be:
> E=0.5*C2*V2^2*break rate/input power.
> > With a high enough inductive coupling to the secondary the inductive
> > coupling to the primary would be negligible?
> Maybe, with a coil mounted close to the top of the secondary. But the
> problem with a continuous load that doesn't exist in a regular system
> continues. Even the tuning conditions would be different.
> > I also agree that your test method is a better one but have you or any
> > coiler been able to make this kind of test? What were the results? In My
> > book I show how Breit, Tuve, Dahl found (1930) their coil to have about
> > efficiency using a similar method as yours. The output voltage was
> > determined by a special calibrated spark device.
> I didn't make this specific measurement. A calibrated spark gap seems
> a good method to measure the output voltage, if the spark is short in
> relation to the size of the spark terminals. Note that any extra
> capacitance introduced by the gap has to be taken in consideration in
> the tuning, and that the gap would have to be calibrated for the actual
> break rate of the coil (remember the results showing that spark length
> becomes dependent on input power for even moderate break rates). With
> a wattmeter at the input and a calibrated spark gap at the output an
> oscilloscope can be dispensed, and the measurement would be quite
> insensitive to interferences.
> > It is interesting that after 100 years the Tesla coil is about the only
> > electrical apparatus for which we do not have an accurate efficiency
> > evaluation.
> As Terry already said, this is because there is no "standard" design,
> no clear definition of what is efficiency for the system, and also
> very few serious attempts to make the measurement.
> Antonio Carlos M. de Queiroz