Re: Power curve


You are experiencing what I call the Tesla coil zener effect.  As you 
increase the input power by increasing the rep rate or the capacitor 
size, you will hit an output spark length limit.  Generally, increasing 
the cap size willy-nilly at the expense of primary turns reduces the 
primary Q and just slags down metal instead of transferring the power 
to the secondary efficiently.  Increasing the rep rate sucks in more 
power and causes the output spark to become hotter and longer to a 
limit.  THE BEST way to increase input power AND output spark is to 
increase the input voltage.  Unfortunately, this is not always an 
option given the availability of standard transformers.  They seem to 
top out at 18KV (especially in dry type).

My plan for my big coil is to voltage double (with diodes and caps) the 
18KV from the transformer to produce about 45KVDC which I will feed to 
the primary cap through a charging choke and series diode (I already 
have these devices).  I made the mistake of increasing cap size to 
0.2uf (50KHZ) and reached a limit of 25 feet of discharge at about 
25KW.  Increasing the power to 50KW by increasing the rep rate or cap 
size just led to molten gap metal with NO INCREASE IN SPARK LENGTH!!

BTW 360w/ft is great!  Keep up the good work.


You wrote: 
>Did Nikola Tesla ever mention anything in his notes about saturation 
of the
>Tesla coil?  I was thinking this weekend that there must be a power or
>efficiency curve that applies to each particular coil configuration.  
Back in
>March of this year, I was using one home made rolled capacitor with 4 
12kv 30
>ma neon transformers and getting 4 feet of spark.  This is 360 watts 
in per
>foot of spark out.  Now, with a commercial capacitor, pole pig, rotary 
>etc. I am gettting just over 6 feet of spark with 8,000 watts in.  
This is
>1,300 watts in per foot of spark out.  If we had a curve of power in 
vs power
>out for this system,  it seems like it would flatten out at or near 
2000 to
>3000 kva in.
>As you slowly increase the power in, I would think the power out is 
>linear for a while and then it gets to a point where the system cannot 
use or
>process any more power.  Is this merelly a function of the secondary?  
>can't see how the primary would be a restriction.
>Ed Sonderman