Re: Resonant charging

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "J. B. Weazle McCreath by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <weazle-at-hurontel.on.ca>
> 
> Hello Coilers,
> 
> Over the weekend I spent conciderable time reading through an old book
> titled "Handbook of Technical Instruction for Wireless Telegraphists"
> which was given to me by a friend who had been a radio operator aboard
> ships back in the spark days.  I found a chapter of it interesting and
> I wanted to share it with the rest of you.
> 
> During the description of a typical spark transmitter, which seems to
> be similar to a Tesla coil in many ways, they describe each component
> of the system and its role in it.  One such component was the inductor
> that was wired in series with the primary of the power transformer as
> we do with our ballasts.  The difference was that they used the choke
> to tune the low frequency (70 Hz.) circuit to resonance with the tank
> capacitor in order to achieve the highest voltage charge in the cap.
> 
> The power transformers they used had a turns ratio of 1:300, whereas
> our NSTs and OBITs are 1:100, meaning they must have been getting a
> very high secondary voltage in a resonant condition.  I'm surprised
> that the plate glass caps that they where using in those days could
> stand that sort of strain.  The whole thing seems to go against our
> policy of trying to avoid a resonant condition, unless under special
> conditions like Gregg's D.C. resonant charging for instance.
> 
> I will be interested, as I'm sure other coilers will too, in hearing
> comments on this setup from some of you more knowledgable chaps on
> the Tesla list.
> 
> 73, Weazle, VE3EAR/VE3WZL

	I have an old 1 kW Thordarson "RS" spark transformer which uses a
movable magnetic shunt to achieve the same effect.  It's much more
rugged than a typical NST.  A second important effect of the "ballast"
is to limit the short-circuit current which flows while the gap is
conducting.

	"They" got away with resonance by fixing the gap length/breakdown
voltage at a safe value for the capacitor and transformer, as anyone can
do now.

Ed 

Ed