Re: chokes

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Greg,
        I think chokes are a bad idea. Just about anything you wind 
will have a half decent Q and will ring with stray capacitances when 
shock excited by the gap discharge. It doesn't take much energy to 
generate voltages well beyond the transformer's apparent output 
rating when small capacitances are involved in a ringing circuit. The 
major cause of NST death is a differential-mode voltage racing back 
down the wiring to the transformer terminals from the gap. A safety 
gap right at the transformer terminals can catch it but a safety gap 
firing should be taken as a warning signal rather than a safety net.
     The other nasty is a common-mode voltage heading towards the 
transformer terminals when a secondary discharge strikes the primary. 
An RC filter incorporating MOVs is a common solution to these 
problems. My approach is to never allow a sec-pri strike, which deals 
with the common-mode problem, and to have just a few inches of wiring 
between the main gap and transformer which effectively deals with the 
differential-mode problem.

Regards,
malcolm

On 3 Oct 2001, at 8:24, Tesla list wrote:

> Original poster: "Mr Gregory Peters by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>
> 
> Thank you all for your individual input on chokes. However, this has 
> served to confuse me even more. Some of you are using a few turns on a 
> 3/4" air core. Some of you are saying not to use an RF choke at all, 
> and yet more are saying to use many turns on a ferrite core. All the 
> repliers have claimed that their particular system has worked very well 
> for them. This is all really confusing. I would very much like to hear 
> what people like Richard Hull and Quick have to say on this matter if 
> they are still out there.
> 
> Richard Quick used to use 18 turns on a 2" ferrite core. However, this 
> is exactly what I was using when my neon died, so I am a bit skeptical 
> of it. Conversely, I ran my coil successfully for months without any 
> chokes at all! help!!!!!!
> 
> Greg.
> 
> 
> 
>