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magnifier vs. classic tc (magnifier modeling)
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From: Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Wednesday, March 18, 1998 1:20 AM
To: Tesla List
Subject: Re: magnifier vs. classic tc (magnifier modeling)
I would like to make a comment:
> From: FutureT [SMTP:FutureT-at-aol-dot-com]
> Sent: Tuesday, March 17, 1998 9:25 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: magnifier vs. classic tc (magnifier modeling)
>
> Antonio, all,
>
> New tests:
>
> I wound a new secondary in order to test the magnifier at k = .51, (for
> the driver). This new secondary is 6 1/2" dia x 3.3" high, 94 turns of
> #24 pvc wire (1.5mH). The same 3" x 12" extra coil was used. Scope
> observation of the ~ 11uS RF beat period showed the effective coupling
> to be about k = .18, which happens to be the same coupling that I used
> in the original classic TC test in the previous posting. Both the maggy
> and the classic coil (which had the same effective k ) performed
> similarly as shown in the table below.
>
> Classic TC Magnifier
> ---------------- --------------
> k = .18 k = .51
> effective k = .18
> beat period ~ 11uS beat period ~ 11uS
> quench -- poor quench -- poor
> (3rd -- 4th notch) (3rd -- 4th notch)
> spark, 3 1/2" max spark, 3 1/2" max
>
> Next, a secondary with a higher inductance of 5mH (but of the
> same physical dimensions as the 1.5mH sec), was installed, to
> verify that the effective coupling would increase as the secondary and
> extra coil inductances became more similar. Tests were done using
> the 13mH extra coil, and also using a 20mH extra coil.
>
> Driver k Effective k (meas) (calc) Lr/Ls Quench
> (extra coil)
>
> .51 (1.5mH) .18 (13mH) .16 8.7:1 4th notch
>
> .45 (5mH) .22 (20mH) .20 4:1 5th notch
>
> .42 (5mH) .29 (13mH) .22 2.8:1 6th notch
>
> It can be seen in the table above that as the ratio of
> inductance between driver and extra coil decreases, the driver k
> and the effective k become more similar. Some of the differences
> between the calc and measured k values may be explained by
> losses in the system, however the last entry seems anomalous.
> More work is needed. Effective k values were measured by
> observation of the beat period relative to Fo.
>
> The series quenching rotary sync gap was used in these tests, and
> it had the same degree of difficulty in quenching in both the classic coil
> and in the magnifier. I.e. quenching difficulty depended only on the
> effective k value, not on the driver k.
>
> Conclusions: Even in these tightly coupled magnifier designs,
> the effective coupling as measured by RF beat durations, was
> much looser than the driver k, and often similar to typical
> classic coil k values. Spark gap quenching demands for the same
> effective k value, were the same in both the magnifier and in the
> classic TC. Overall performance was similar, maggy vs. classic TC.
>
> Thanks Antonio for the calculations and comments regarding my
> prior posting.
>
> Comments welcomed.
>
> John Freau
Thanks to Antonio for looking at modelling and thanks for your
experimental results. This opens the way for anybody to build a mag
easily and run it off NSTs using plain vanilla gaps. I must say,
after reading both the CSN and the Corum's material, this is a
somewhat unexpected and pleasing turn of events. The big
disappointment is in finding there is not much difference between the
two and three coil systems save that the resonator is well clear of
its primary and therefore insulation is solely Vout related without
the added difficulties due to corona in the vicinity of the primary. I
will set mine up in the weekend and give it a real blast.
Regards,
Malcolm