Potential difference vs. spark length vs. break rate

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

Original poster: "Dr. Resonance by way of Terry Fritz <teslalist-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>


This is an snip from an off-list discussion that John Couture and I have 
been having regarding potential difference, spark length, and break rate.

One area where there seems to be complete confusion is regarding break 
rate.  The most important point to consider is that break rate and spark 
length growth from an increased break rate has absolutely nothing to do 
with potential.

The output potential is a fixed value and depends on the circuit components 
and parameters.  Spark length can depend on a variety of parameters 
including break rate and power input.  Higher power can recharge the 
primary capacitor bank and deliver the ability for the system to be 
operated at a higher break rate to create longer sparks.

Most important, the potential (voltage) developed is completely independent 
on the break rate and power level.

A lower available power, ie, charging current rate, would mean the 
capacitor would charge up to a certain voltage value in a longer period of 
time.  When the cap reaches a certain value of potential, which is 
determined by the spark gap setting, it fires at the same potential as a 
large transformer supplying a high rate of current.

While a break rate does generate longer sparks it is not really important 
with regard to the discussion of potential.

The voltage developed is usually dependent on the standard equations of the 
primary voltage x the sqr Ls / Lp.

The best way to measure Tesla coil potential is to rectify the xmfr output 
and then use a 10 or 20 Meg resistance in series with the sparkgap or (even 
better), use an ignitron to allow precise triggering of the spark gap.  The 
system is operated in a single shot mode and the spark length recorded 
betweeen standard electrodes like a 1/2 inch rod gap or two spheres, ie, 10 
cm or 100 cm.

The actual voltage in this single shot mode is the exact same voltage as a 
unit operating at a high break rate.  This potential can be accurately 
measured and recorded.  The high break rate will produce longer sparks but 
the actual potential (Volts) does not increase.  It remains constant 
depending on the circuit parameters.
This fact allows for easy and accurate measurement of any system.

What is missing from the Tesla coil picture is an accurate analysis of the 
spark length based on break rate.  I hope to be able to do some of this 
research later this summer and present a graph indicating break rate vs. 
power vs. length.  I intend to use one of our standard model M-150 units to 
take the measurements.  This system operates at 7.5 kVA and produces 8 ft. 
long sparks.

Dr. Resonance

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913