DRSSTC: Magnifier Vs. 2-coil System

Created 5/6/05

I have lately been spending a great deal of time with the DRSSTC magnifier.  My first DRSSTC magnifier can be seen here.  This is my experimental coil for now. It's easier to work on a smaller scale since I run the coil indoors.  The data taken below is with this particular setup.

At first glance, the magnifier has seemingly little to offer over a 2-coil system.  The most desirable effect is that it moves the sparks away from the primary coil and electronics.  After hours of experimenting with tuning and coupling, I decided it was time to write down some numbers and try to analyze the efficiency of the magnifier setup.  So today (May 6, 2005) I did a comparison between a 3-coil and 2-coil system at various performance levels.  I apologize for the lack of organization of the data I present here, it's really just to help open discussion about this topic.  Note: maximum coupling was determined by the point where flashover between the primary and secondary would occur (though rare).  I don't have exact K values due to the unconventional primary setup I used, I might try to figure out the K at a later date, but for practical purposes, we can assume the max K (overall) was about .24.  I should also mention that the BPS was set to 120 for all experiments.

The following data was taken for a 2-coil system.  The K was around .22 (estimate) and held there for all tests with the 2-coil system (this was the highest K achieved before serious insulation issues came about).  The secondary is 11"x4.5", 30awg winding.  The toroid used is 16"x3".  The tuning changed throughout these runs, gradually tuning lower on each data entry.  This caused the time period before a notch to occur to lengthen.  I set the On period so that it ended with a notch as this seems most efficient.  The below data is averaged from some 12 tests, I think it conveys enough information for some sort of comprehension.

Spark Length (inches) Primary Current (peak amps) On period (uS) Power recorded (watts) % of 140VAC input voltage
24 300 90 200 100
30 350 110 320 100
35 450 150 500 95

Below is the data for the 3-coil system.  Again, data is averaged.  K is kept in the medium to high level (.2-.24 overall, not driver K), tuning gets lower as you move down the list (again, lengthening the time before notching occurs).

Spark Length (inches) Primary Current (peak amps) On period (uS) Power recorded (watts) % of 140VAC input voltage
24 350 100 200 100
30 425 120 350 90
36 450 120 420 100

Overall, the performance of both setups were similar.  We can see that the spark length matches that of a *highly* efficient spark gap coil for the input power (according to the Freau formula: Spark length = 1.7*sqrt(power) ).  The magnifier was able to produce longer sparks (up to 40", but at nearly 650W!), but this is at the expense of a larger setup overall.  The magnifiers efficiency seemed to pick up at higher power levels.  I think it might come down to how hard you try to push a small coil like this.  Driving a larger coil might improve efficiency, that remains a test for a later date.