RE: FW: Re: Tesla Coil Efficiency Test

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

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

Hi John,

On 16 Jun 2002, at 22:16, Tesla list wrote:

> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
> 
> 
> 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
> zero?
> For the TC efficiency shouldn't this be the integrated and RMS
> output/input,  otherwise, the efficiency would be an instantaneous or peak
> type?
> 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
> evaluation.

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.

Regards,
malcolm

 
> 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
> past
> > with varying results. In my Tesla Coil Construction Guide book I show a
> test
> > 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
> is
> > found by the intensity of an incandescent lamp inductively coupled to the
> > secondary coil.
> 
> There are several problems with this technique. First, the maximum
> voltage
> 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
> to
> 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
> inductive
> coupling.
> 
> 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
> 
> 
> 
> 
> 
> 
>