Re: Potential difference vs. spark length vs. break rate

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

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 12:31 PM 5/22/2003 -0600, you wrote:
>Original poster: "Dr. Resonance by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>
>
>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.


This sounds good.  I can think of some reasons why the voltage might not be 
the same in multiple shot vs single shot mode.  It might be useful to see 
if we can come up with experiments to determine if they are something that 
needs to be factored in.

1) The voltage on the primary cap, just before the spark gap fires, might 
be different than in single shot mode.  A scope and a HV probe can 
determine this.

2) Electrode heating in the spark gap might result in a somewhat different 
gap characteristics "under load".  This should also be quantifiable, since 
the voltages and currents at the gap are accessible and reasonable to 
measure without perturbing the system too much.  If anything, the heating 
of the gap might decrease the voltage drop, but, could also change the 
timing relative to the AC supply.    Running the coil off a regulated DC 
supply would be useful here, but, I don't know that I'd want to try and 
build a 10 kW DC supply regulated that well.


3) Are there some dynamic effects with respect to corona losses at the top 
load?  This is the tricky one, but, I think that the dominant effect will 
be the one you're already measuring: spark length.




>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