From: Paul
Date: Thu, 15 Feb 2001 18:55:19 +0000
Subject: Re: [TSSP] Top voltage testing
Terry wrote:
> Winding length = 26.125 inches
> Diameter = 4.25
> #24 wire = 0.0201 diameter
> Turns = 1180?
> Rdc = 34.0
> Ldc = 22.1mH
> Height off ground plane = 0.35 inches
Putting these dimensions into the model gives
measured modeled error
Rdc: 34.0 ohms 34.2 ohms +0.6%
Ldc: 22.1 mH 22.54 mH +2.0%
(I used the measured Ldc, rather than the calculated, in what follows.
Are we seeing reduced Ldc due to eddy current coupling to the foil?)
f1: 358.3 kHz 357.3 kHz -0.3%
> Using the Tek 5100 probe on the top I get:
> F1 = 311.3kHz
> Iin = 0.20815mA
> Vtop = 7.9465V
>
> I calculate that the H/D is 6.1471
> Vtop / Iin = 38168 ohms
> Zes = 19.5135mH or 88.3% of Ldc
OK, I find that 3.11 pF of probe capacitance is necessary to reproduce
this f1:
measured modeled error
f1: 311.3 kHz 311.3 kHz 0.0% Ctop adjusted to match
Zft: 38168 ohms 34903 ohms -8.6%
Les: 19.5135 mH 17.8 mH -8.6%
Roughly speaking, the model predicts Les at 80% of Ldc, and you're
splitting the difference at 88% Ldc,
Can you check that you have an f3 lurking at around 871 kHz for the bare
coil and 829 kHz in the probed coil.
How come the base current dropped so much between the bare and probed
readings?
Cheers,
--
Paul Nicholson,
Manchester, UK.
--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.