# 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

```