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RE: FW: Re: Tesla Coil Efficiency Test
Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>
On 16 Jun 2002, at 22:16, Tesla list wrote:
> Original poster: "John H. Couture by way of Terry Fritz
> Antonio -
> I agree that this test loads the secondary and reduces the output voltage.
> However, don't we want to have a secondary load so the useful output is not
> For the TC efficiency shouldn't this be the integrated and RMS
> output/input, otherwise, the efficiency would be an instantaneous or peak
> With a high enough inductive coupling to the secondary the inductive
> coupling to the primary would be negligible?
> I also agree that your test method is a better one but have you or any other
> 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 25%
> efficiency using a similar method as yours. The output voltage was
> determined by a special calibrated spark device.
> 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
That is probably because the load varies so widely and under less
than ideal conditions (energy trades being allowed to persist), a lot
is lost in the gap. One-way transfer efficiences are relatively easy
to measure and can get well into the 80% range despite the gap. If
the energy resident in the secondary after the initial transfer is
dumped into a load before it can get back to the primary, the 80%
figure would closely apply. None of this takes any account of the
wallplug to primary cap losses.
> John Couture
> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Saturday, June 15, 2002 9:06 PM
> To: tesla-at-pupman-dot-com
> Subject: Re: FW: Re: Tesla Coil Efficiency Test
> Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>
> Tesla list wrote:
> > Original poster: "John H. Couture by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
> > Many coilers have tried to measure the efficiency of their coils in the
> > with varying results. In my Tesla Coil Construction Guide book I show a
> > method that I used for a small TC that appeared to work for TC efficiency.
> > However, I am now having second thoughts about the test results and wonder
> > what other coilers think about this type of test.
> > The input energy is found by the setting of the variac. The output energy
> > found by the intensity of an incandescent lamp inductively coupled to the
> > secondary coil.
> There are several problems with this technique. First, the maximum
> and maximum current from the transformer don't have a so direct relation
> to the actual power going into the system. Second, with a lamp coupled
> the secondary, the Tesla transformer will be heavily loaded, and all the
> waveforms will be different from the normal. The lamp may be also taking
> energy directly from the primary, and not from the secondary, with
> A correct method for efficiency measurement would be to first measure
> what is the peak primary voltage V1 where the primary gap fires,
> and then to measure what is the maximum voltage level V2 reached at the
> secondary terminal, without breakout. The efficiency would then be:
> E = C2*V2^2/(C1*V1^2)
> where C1 is the primary capacitance and C2 the secondary capacitance
> (combination of Ccoil with Cterminal, almost their sum).
> An oscilloscope can make all the measurements, with an adequate
> HV probe or attenuator fo the primary voltage and an antenna for the
> secondary voltage, with a calibration obtained by exciting the secondary
> terminal directly with a signal generator at the resonance frequency.
> Complicated, but I don't see shortcuts. This is a difficult measurement.
> Even with all care, heavy interference is expected.
> Antonio Carlos M. de Queiroz