# Re: Harmonics

```In a message dated 1/13/99 2:18:31 AM Pacific Standard Time, tesla-at-pupman-dot-com
writes:

<SNIP>
> What you are talking about is resonant rise. A spark driven Tesla coil
>  does not experience resonant rise. A Tesla coil should be viewed more like
a
>  lightly coupled transformer.

I have to disagree with you here.  The coil is indeed a loosely coupled
transformer, but resonant rise DOES exist.

<SNIP>
>  Not all of the primary energy is transfered into the secondary during one
>  oszillation, so you want the tank circuit to be able to "swing" a few times

Since it is loosely coupled, you are right that not all of the energy is
transferred in one oscillation.  And you are also right as you stated that all
the primary energy will be transferred to the secondary over a period of
cycles. This builds upon the previously stored energy in the secondary
circuit, and this is resonant rise!  Resonant rise is the condition in which
the energy from the power source builds upon the energy already stored in the
reactive components in a series LC AC circuit.

>  I think a better picture of a spark gap driven Tesla coil would be a hammer
>  and a bell. Your hammer is the primary circuit and the bell is your
> secondary coil. The bigger the hammer, the "harder" the bell rings
<SNIP>
If you view it this way, then each cycle of the oscillation of the tank
circuit ("hammer") lightly taps the secondary circuit ("bell"). The hammer
taps the bell at the same frequency the bell is ringing at, so as to build
upon the intensity of the ringing. Once again, this is exactly what resonant
rise is.  This is also just another form of the "pushing a swing" analogy.
However, resonant rise in a TC behaves a little differently than in a simple
series LC circuit with constant power source.  In a Tesla coil Vout does not
equal QE, but rather (joules out) = (joules in) - (losses) and V is found by
root(J / Cs).  Resonant rise reaches its peak when the power source (primary
circuit) is drained.  At this point, the secondary begins acting as the power
source (hammer) to the primary circuit (now the bell).  Then, energy is
gradually transferred back to the primary by resonant rise.

Matt Behrend

```