# 60 vs. 30 ma

```From: 	Gary Lau  18-Jun-1997 0810[SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent: 	Wednesday, June 18, 1997 8:10 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: 60 vs. 30 ma

>>If you add larger transformers, you can certainly also increase
>>the capacitance to take advantage of the higher charging current.
>>All I'm saying here is you do not have to increase the capacitor
>>value when higher current transformers are added.  Some folks
>>seem to think one requires the other.

>Actually you do have to increase the capacitor size if you increase
>the charging current otherwise you will not be using the additional
>current. Realize of course this assumes that you were already using
>the largest practical size capacitor for the charging current. The
>capacitor is really the controlling factor as to how much power we
>can cram into a given Tesla coil.

It would seem to me that if one switches to a transformer with
twice the current rating, using the same capacitor, that the
capacitor would simply charge up to the spark gap voltage twice
as fast.

Modeling the transformer as a voltage source Vt and series R.
In a series V-R-C circuit, solving for the time to charge the cap
to a certain voltage Vc, t = -RC ln((Vt-Vc)/Vt).  Doubling the
transformer current rating would halve the R value.  From
equation above, this would also halve the time for the cap to
charge to the spark gap voltage, Vc.  Thus the same capacitor
would dump it's load into the primary twice as often, delivering
twice the power as with the smaller transformer.

What I have not considered is, is there an optimum rate at which
to dump energy pulses into the tank circuit?  I'm sure that this
is related to one's gap quenching time and tank ring-down time.
But then the conventional wisdom of matching one's capacitor
reactance to the transformer's impedance doesn't consider this
either.

Gary Lau
Waltham, MA

```