Re: Pushing Neons: Extra Current (fwd)

---------- Forwarded message ----------
Date: Tue, 28 Jul 1998 08:01:11 -0400
From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Pushing Neons: Extra Current

Terry, Marco,
The reason there is more current being consumed when the gaps do not
fire is that the transformer has charged the capacitor UP to say
some large *positive* voltage, and now, before it can can charge it
to some *negative* voltage it has to first get it discharged 
to a zero level. Normally the gaps firing and dumping energy
into the primary takes care of this. But when the gaps do not
fire, the transformer bravely tries to reverse the polarity anyhow.

Obviously while the transformer is trying to discharge the cap
it just charged, it is doing MORE work than it did simply
charging it. If the cap is just the right size you can also get 
a resonant charging affect that can cause the output voltage to
rise significantly. This can over-stress the transformer and caps,
and is often the cause of failure in Tesla Coil systems.

Hope this helps.
Fr. Tom McGahee

> ---------- Forwarded message ----------
> Date: Mon, 27 Jul 1998 11:22:19 +0300
> From: Marco Denicolai <marco-at-vistacom.fi>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: Pushing Neons (fwd)
> At 22:35 25/07/98 -0600, you wrote:
> >
> >
> >---------- Forwarded message ----------
> >Date: Sat, 25 Jul 1998 17:53:00 -0600
> >From: terryf-at-verinet-dot-com
> >To: tesla-at-pupman-dot-com
> >Subject: Pushing Neons
> >
> >Hi All,
> >        I have been playing with a high performance charging circuit design
> >that uses a 15kV 60 mA neon transformer.  I have the design ironed out so
> >that when the input voltage is 120 volts, the current is about 8 amps.  The
> >output voltage is 15kV and the current is 60 mA (all RMS values).  This is
> >charging a 20nF cap to 21 kV peak.  So everything is within specifications
> >of the components.  
> >
> >        The first problem is when the gap fails to fire or you are turning
> >up the variac and the gap hasn't fired yet.  Without the gap firing, the
> >neon's input current is 20 amps.  The output voltage is still 15kV but the
> >output current is 115mA. 
> Please, mind my stupid and simple question, but I don't really understand why
> if the gap doesn't fire the NST sinks higher current. Do you mean that if the
> gap doesn't fire you reach a point of the AC half-wave (charging the primary 
> capacitor) that results in 115 mA of charging current?
> ________________________________________________________________________
>  Marco Denicolai                   Vista Communication Instruments, Inc.
>  Hardware Development Manager      www.vistacom.fi   
>  marco-at-vistacom.fi                 Kaisaniemenkatu 13 A
>  fax:    +358-9-622-5610           SF-00100 HELSINKI
>  phone:  +358-9-622-623-15         Finland
>    Remember, Murphy was an optimist! I am not...
> ________________________________________________________________________