From: Paul
Date: Wed, 11 Jul 2001 16:13:58 +0100
Subject: Re: [TSSP] Thor base current measured
Hi Marco,
Thanks very much for the data, a very nice result. So far I've only had
time to do a low-resolution run of the model, which gives a rough
comparison of the base currents,
http://www.abelian.demon.co.uk/tssp/md110701/md1.gif
with a zoom into the first secondary beat,
http://www.abelian.demon.co.uk/tssp/md110701/md1.gif
The model's mode 3 is around 5% out in frequency, which means that by
the end of the first beat, the mode 3 phase is almost opposite to what
it should be, as can be seen in the first notch. The reasurring thing
is that the higher modes really *are* being excited by roughly the right
amount. We've first saw this on the base current comparison from
Terry's coil,
http://www.abelian.demon.co.uk/tssp/tfss270501/
but the effect seems to be a little more prominent with Thor's higher
k-factor. I'm now prepared to believe that the higher mode excitation
predicted by the model is a genuine result of the physics and not an
artifact of the software. The amplitudes are about right, and with
sufficient attention to detail, we should be able to get a phase match
on the 3/4 wave and 5/4 wave modes at least as far as the first notch.
I'll do an over-night run of the simulator, at higher resolution.
Any idea what's causing that heavily damped ringing at around 800kHz at
the start of the event? Don't suppose you have a grid-dip oscillator to
hand? Doesn't seem to soak up too much energy - modeling 14kV on the
primary is giving just about the right peak base current.
Here's part of the description file that I'm using for Thor, can you let
me know if anything is incorrect?
toroid {
outer_radius 0.7575 ; Distance from center to outer rim.
inner_radius 0.5575 ; Distance from center to inner rim.
height 2.85 ; Distance of center above ground plane.
}
primary {
radius1 0.275 ; Inner radius
radius2 0.545 ; Outer radius
height 1.045 ; Above ground plane
turns 9.5
tap 7.5
conductor 0.4e-2 ; 8mm diameter
cap 96.7 nF
res 1.0 ; Primary circuit resistance - a guess
volts 14 kV ; for md110701
;;;volts 18.35 kV ; Nominal bang voltage
}
secondary {
radius 0.20 ; Radius of coil
length 1.575 ; Length of coil
height 0.995 ; Distance of base of coil above ground plane.
inductance 0.0802 ; The measured inductance, for info only.
turns 939
resistance 11.2 ; Measured resistance at DC.
conductor 0.725e-3
former {
material hdpe
thickness 0.02
}
}
Cheers,
--
Paul Nicholson,
Manchester, UK.
--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.