From: "Malcolm Watts"
Date: Thu, 26 Oct 2000 08:34:11 +1300
Subject: Re: [TSSP] NSVPI - Latter Results
On 25 Oct 00, at 7:14, Paul wrote:
> I've recomputed the model of Terry's coil having adjusted
> the E-field loss factor to give the measured Q of 70, and I've
> altered the inductance to 75.1mH
>
> I expected that the raised inductance and the increased loss
> would dispose of some of the residual few percent error in the
> top voltage estimate as compared with the integrated value
> from Terry's gradient measurements.
>
> In fact this hasn't happened. Short of tampering with the
> capacitance distribution produced by the laplace solver I
> can't get rid of the residual error. The plummeting Q has
> not noticeably reduced the transimpedance so the predicted
> topvolts remains on the high side of the measurement.
>
> One thing of note is that now the loss factor has been set
> to match the given Q, the input impedance prediction comes out
> at 713 ohms - in accordance with Terry's measurements. Previous
> attempts to make both Q and Zin match simultaneously failed since the
> extra loss was imposed by artificialy increasing Rs. Attributing all
> the extra loss to the E-field does the trick nicely, and gives me a
> bit more confidence in the stored energy and Q factor calculations.
>
> Under these conditions, the energy loss breakdown in the secondary is
> 83% into the E-field, presumably mostly sonotube, and 17% into the
> coil resistance. The overall E-field loss factor required to drop the
> Q to 70 is a whopping 0.0139, considering the sonotube takes up a
> small volume of the field, the sonotube loss itself must be very high
> indeed.
That is an encouraging find. I think it lends some credence to
the kinds of Q's I was measuring on both the PVC and HDPE
coils. It means that very good coils can easily be built.
I enjoyed reading your pn1310 (?) paper. The arguments
look prima facie reasonable to me and the fact that they fit a
measured profile is most encouraging.
I am enjoying participating in a group which is putting
some real science into the "art" of coiling. It is nice to
think that at the end of the various threads of investigation
a coil will be designable to a specification. It is time for
suck-it-and-see approaches to end in my opinion.
Regards,
Malcolm
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.