Re: stepped leaders (was Safety FAQ...)
> Robert Stephens wrote:
> I can't seem to locate where I misplaced your paper to in order to
> refresh myself, but I'm mentally recalling the dimensions and method
> of construction of the toploading toroid as being very close, in fact just
> slightly smaller to the one I put on my largest coil to date. Mine
> was 15"X67", made from a custom manufactured single 33 foot length of
Yes, my toroid is 13"X65", and will leak about 750uA with 200kVDC applied from
a test power supply. (Quite an audible amount of hissing.) I couldn't go much
higher, but I got the distinct impression that it would certainly let loose at
twice that voltage.
> My point is, did you actually measure the terminal voltage achieved,
> or are you relying on a calculation by whatever CAD program you use.
> The charts supplied in your paper appeared to be CAD program generated
> rather than the output of a plotter hooked to a measuring voltmeter.
The 550kV is an estimate based on actual measurements. Here's how I came up with that:
I ran the coil at 1 pulse per second, by putting a big resistor string in series with
the DC power supply. A grounded sphere was brought towards the toroid, until it
was just close enough to draw an arc, at 1pps. This arc distance was about 2 feet.
Then with the coil off (toroid grounded), HVDC from the test supply was applied to the
sphere, with the sphere in the same position. It took about 275kVDC in order to bridge
the same gap. At this voltage, I believe that the meter is good to +/- 20%. At 1pps
however, the primary voltage is half of normal, due to the resonant charging circuit.
So, for normal operation, the output voltage is probably about 275kV x 2 = 550kV.
I feel that this number is roughly correct, as it correlates well with the secondary
current, which measures about 25A peak during operation, 10 to 15A during 1pps tuning.
The secondary is 20000 Ohms at resonance (2pi x 62kHz x 52mH), and 20000 x 25A = 500kV.
PSPICE gives values anywhere from 300kV to 750kV, depending on what secondary model
I use! I feel that I still don't have a good model.