FW: Gap Losses
From: richard hull[SMTP:rhull-at-richmond.infi-dot-net]
Sent: Monday, August 25, 1997 3:01 PM
To: Tesla List
Subject: Re: Gap Losses
At 08:23 AM 8/22/97 -0500, you wrote:
>From: Greg Leyh[SMTP:lod-at-pacbell-dot-net]
>Sent: Thursday, August 21, 1997 2:58 PM
>To: Tesla List
>Subject: Re: Gap Losses
>I wish that someone could have had hollered at me back in 1989 when I designed
>my present 50kW coil. The whole design of the primary pivoted upon the working
>resistance of the rotary gap, which I had to calculate from textbooks since
>I could not find anyone who had ever actually measured the R of an TC
>My calculations yielded about 0.25 ohm for the gap at 3000A, so I chose a
>primary surge impedance of 5.3 ohm, which would yield an unloaded Q of over 20
>and provide a reasonable tradeoff between primary Q and transformation ratio,
>even if the Rgap was as high as 0.4 ohm.
>As luck would have it, once the coil was built and tested the actual _measured_
>working resistance of the gap was 0.65 ohm! But the thing ran OK, and so I
>left well enough alone for the time being. Then, when I finally gathered the
>initiative (and the copper) I started hacking on the primary circuit, and
>raised the surge impedance to 15 ohms to regain the desired Q of 15 to 20. Now
>the coil requires only 35kW instead of 50kW in order to achieve ground strikes.
I was not hollerin' at you! That was your first shot. Most of us live and
learn. I was hollerin' about certain "big boys" in "the business" for years
who seemed to not get the message after the 50th system. Some are now
wakin' up though.
Richard Hull, TCBOR
As regards what is the optimum surge impedance..... I honestly believe it is
like everything else in this messy business...firmly planted in ever
It is part of the art.
A question to your question what is really high? ...Low? It is as much
power related (relates to frequency too) as to some magic number. You
effectively said this earlier.
I feel I have observed the need for magnifiers to have much lower average
surge impedances in their primary tanks than two coil systems at similar powers.
Stands to reason anyway.