Re: 2 questions on resonance

To: tesla-at-pupman-dot-com
Subject: Re: 2 questions on resonance
From: "Dr. Resonance" <Dr.Resonance-at-next-wave-dot-net> (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Wed, 14 Apr 1999 19:07:49 -0600
Approved: twf-at-verinet-dot-com
Malcolm & Terry:

As you guessed a phase lag is being created by the xmfrs leakage inductance
which shifts the point at which the cap receives its charge.  If you
measured the potential at the xmfr primary with a standard NST with internal
leakage paths then you will see the phase shift as you mentioned.

If you are running a pole pig and measure the phase shift before the current
limiting inductor you will also see the phase shift.  If you measure the
potential at the xmfrs primary after the current limiting inductor there
will be less phase lag.

If you want a true picture then use a TekTronics model 6015 probe which
contains a resistive divider and cap divider network.  You then measure the
high potential waveform directly on the HV cap itself (probe good for 40 kV)
and you will see a direct 1:1 correspondence between the firing point on the
synchro RSG and the peak potential across the cap.  These probes are
available surplus for around $150 and are very worthwhile investment to any
experimenter doing serious HF measurements.  This is what we use in our
shop.

Regards,

Dr.Resonance-at-next-wave-dot-net



-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Monday, April 12, 1999 9:07 PM
Subject: Re: 2 questions on resonance


>Original Poster: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
>
>Hi Terry,
>
>> Original Poster: Terry Fritz <twf-at-verinet-dot-com>
>>
><snip>
>>         The maximum firing voltage actually occurs about 40 degrees AFTER
the
>> peak in the primary wave form.  That sure "sounds" funny but this is the
>effect
>> my last paper mentioned.  If I try to set the sync gap to fire on the
>peak, the
>> firing voltage drops drastically.  This is a hard thing to explain
without
>> "live" computer or scope wave forms in front of one.
>
>I'd suggest that in effect this is tuning the charging period to the
>resonant frequency of the NST inductance and the larger cap. The
>notes about erratic firing and apparent unsuitability of using a
>large cap value with a static gap are well taken. I've seen this for
>myself. I suggest that this phenomenon is closely associated with the
>research done by Jameson in the ROTJIT program and explanatory notes
>where off-frequency charging resonance causes conflicts with the
>mains frequency and conspires to give erratic effects in some rotary
>systems. I think the transformer actually requires the gap short at
>firing time in order to assist energy storage in its leakage
>inductance. A few maybes in the melting pot. I now can't see any
>alternative but to switch to a sync gap to get the best from a NST.
>
>Malcolm
>