Gaps and tank Q

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: Gaps and tank Q
From: Tesla List <tesla-at-stic-dot-net>
Date: Sun, 8 Mar 1998 16:38:08 -0600
Approved: tesla-at-stic-dot-net

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From:  Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent:  Sunday, March 08, 1998 3:57 PM
To:  Tesla List
Subject:  Re: Gaps and tank Q

Hi John,

> From:  FutureT [SMTP:FutureT-at-aol-dot-com]
> Sent:  Friday, March 06, 1998 8:05 AM
> To:  tesla-at-pupman-dot-com
> Subject:  Gaps and tank Q
> 
> All,
> 
> Has anyone determined how much the gap losses are likely to increase
> when using 8 to 12 multiple series gaps, either static or rotary,
> compared to a smaller number such as two?  

The higher the primary voltage, the less significant more gaps becomes
as each has a relatively small voltage drop associated with it. For 
gap currents significantly greater than 10A the drop seems to bottom 
out at a pretty low value. For coils running with Vp's on the order of 
8kV I wouldn't use more than two in series but for something running
18kV I'd be happy with six to help quenching.

> Probably a high surge impedance primary is more tolerant of multiple
> gaps, since the the gap losses tend to be a smaller percentage of
> total tank losses in the high surge impedance primary case.  Has 
> anyone looked at this?

The surge impedance appears to dictate the decrement slope 
(assuming Rp is negligible which it usually is) and in conjunction 
with Vp largely dictates gap current which then dictates loss per gap
(higher current = higher loss). However, the loss is demonstrably 
pretty small compared with peak tank power if surge impedance is high. 
No exact figures sorry. I am planning to take a day off work soon to 
do some measurements on a mag system I'm working on so I could do 
some on this as well.

Malcolm