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Re: rotary gap problem (fwd)



---------- Forwarded message ----------
Date: Thu, 12 Feb 1998 06:19:46 -0800
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: rotary gap problem

Tesla List wrote:
> 
> ----------
> From:  dwight duncan [SMTP:duncand-at-ccsalpha2.nrl.navy.mil]
> Sent:  Wednesday, February 11, 1998 8:05 AM
> To:  tesla-at-pupman-dot-com
> Subject:  rotary gap problem
> 
> Hi all,
> 
>     Mr John Freau made the suggestion of making my stationary electrodes
> flat wrt. the rotor disk.  I gave this a try and there was a slight
> improvement.  I also took out every other electrode on my disc to a new
> total of 8.  The motor is running markedly faster and is rated at 2400 rpm
> and is of the brushed variety.  Still my safety gaps are still firing
> almost continually.
>     My supply consists of two 5 Kv 300 ma transformers put in series with
> the center or commons on the HV side grounded.  This gives me 10 Kv at 300
> ma.  Just after the transformers are 4 nf caps in parallel to ground on
> each side of the output.  next is a laminated iron core common mode choke
> with each side at 4 mH.  Finally is the safety gap with a ground post in
> the center and it was set so it would not fire when the feeds were
> disconnected from the tank.
>     John mentioned the problem may be in the toroid.  Using the statement
> from Richard Hull I went for as large of a toroid that I could make.  I is
> a 16" dia. disc with a 4" aluminium dryer hose wrapped around the OD.  I
> did an order of magnitude calculation and came up with 25 pf.  This
> calculation made some assumptions that may not be valid.
>     Anyway this is my whole system and I am running out of ideas for the
> cause of this problem and to John or anyone that might have some insight
> please reply and any or all comments are greatly appreciated.
> 
> PS.  The secondaries resonance is measured at 220 KHz and the primary is
> tapped out at almost five turns. My tank capacitance is .08 micro F.(from
> Maxwell)
> 
> Thanks,
> 
> Dwight

Dwight,

Aha!! I misunderstood how your system was configured before. Your
problem is that the safety gaps should be directly connected between the
HV transformer output leads and the RF ground so that anything nasty
that still makes it through your RF filters will then be killed by the
safety gap. In your present configuration, you've got the safety gaps in
parallel with your rotary...

-- Bert --