RE: "Gas burner" corona from STSG driver

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

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-compaq-dot-com>

Hi John:

You raise an interesting point.  While I firmly believe that the terminal
secondary voltage is strictly AC, with no DC bias, your mention of the
secondary base current made me stop and think.  It is the asymmetric
conduction of corona from the secondary and top load that causes a DC
charge to be generated.  It is possible that the secondary _current_ can
have a DC bias, due to coronal rectification, while the secondary voltage
is strictly centered about zero.  Since the corona is external to the coil,
I believe it is correct to say that the coils generate unbiased AC, but
your base current measurement showing a DC bias is probably quite real.
Just like a circuit with a xfmr secondary in series with a diode and cap.
The transformer voltage is unbiased AC, but the current is DC-biased AC.

Gary Lau
MA, USA



Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>


Kurt -

When I did this TC test with the electroscope I also connected an ammeter to
the bottom of the secondary coil to read the DC current. The direction of
the current indicated the secondary terminal was negative.

Have you ever done this type of test with an induction coil? I am enjoying
your Induction Coil web site.

John Couture

-----------------------------


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Saturday, January 05, 2002 7:25 AM
To: tesla-at-pupman-dot-com
Subject: Re: "Gas burner" corona from STSG driver


Original poster: "Kurt Schraner by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<k.schraner-at-datacomm.ch>

John, Gary -

To my knowledge, what has been used for X-Ray were induction coils, not
Tesla coils. Probably John meant this (please correct me if I'm wrong)?
- The design of those inductors took into consideration, to make the
secondary sparks voltage-waveform with as low "inverse" as possible,
meaning a waveform with high DC part. This is elucidated i.e. in
M.A.Codd, Induction Coil Design, E.& F.Spon, London 1922, reprint
obtainable by PV-Scientific.

Cheers,
         Kurt

Tesla list wrote:
>
> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Gary.Lau-at-compaq-dot-com>
>
> Be careful how you state this.  The terminal voltage of a Tesla coil is
AC.
>  The secondary oscillations are centered about zero volts.  Insulated
> objects near the secondary will develop a DC or static charge deposited
> upon them, due to the asymmetric conduction (a.k.a. rectification) of
> corona.  This is what an electroscope will indicate.
>
> Gary Lau
> MA, USA
>
> Original poster: "John H. Couture by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>
>
> Allan -
>
> Not correct. Tesla coils were used by hospitals to make X-Rays (DC needed)
> until the thirties when other devices became available. Tesla said that
> Tesla coils could produce DC because the negative output was greater than
> the positive output. You can prove this by charging an electroscope with a
> TC and checking the type of charge.
>
> John Couture