Re: Superconducting tesla coil (fwd)

To: tesla-at-pupman-dot-com
Subject: Re: Superconducting tesla coil (fwd)
From: Tesla List <mod1-at-pupman-dot-com>
Date: Sun, 29 Mar 1998 21:45:48 -0700 (MST)
Approved: mod1-at-pupman-dot-com


---------- Forwarded message ----------
Date: Sun, 29 Mar 1998 19:19:21 -0600
From: Bert Hickman <bert.hickman-at-aquila-dot-com>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Superconducting tesla coil (fwd)

Tesla List wrote:
> 
> ---------- Forwarded message ----------
> Date: Sun, 29 Mar 1998 18:17:41 -0500
> From: "A. Scott Chesnick" <chestnic-at-mail.cvn-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Re: Superconducting tesla coil (fwd)
> 
> Tesla List wrote:
> 
> > ---------- Forwarded message ----------
> > Date: Sun, 29 Mar 1998 13:38:30 EST
> > From: ESchulz531 <ESchulz531-at-aol-dot-com>
> > To: tesla-at-pupman-dot-com
> > Subject: Superconducting tesla coil
> >
> > Just as an idea what would happen if you used superconductive wire for the
> > secondary and the primary?  Q would go towards infinity, so how would you tune
> > it?  There would be no losses due to resistance so you could use really small
> > wire and have lots of insulation.  I wander if anybody on the list has funding
> > to try this?
> >
> > Anyway when I win the lotto I will let you all know how it works. :)~
> >
> > Erik Schulz
> > ESchul531-at-aol-dot-com
> 
>   The wire would have limited current penetration due to skin effects even at the
> frequency a telsla coil works at. The coil Q would go through the roof. The q
> would then be limited by the capacitor Q dielectric losses and the resistance of
> the leads to the capacitor to the coil. There is also a limit to the amount of
> current a superconducting wire can carry before it goes normal and the
> superconducting state braks down.

Erik,

Interesting thoughts, Erik. Some unfortunate realities:

1. The effective primary Q is dominated by the spark gap, not by the
primary winding or tank cap. Making the primary superconducting will not
greatly improve the overall Q of the primary under disruptive operation.
However, it CAN make a substantial difference in a CW coil.

2. The total secondary LC circuit includes an interconnection to the
earth (which forms the other "plate" of the secondary self-C and
terminal capacitance). A good RF ground (most are not, BTW) would be in
the 5-10 ohm range, and will govern the non-breakout Q of the secondary
system.

3. Once you get top breakout, the secondary Q goes into the dumper
precisely because you are now rapidly losing energy to streamers. The
"effective" secondary Q typically drops to around 10-20 under heavy
streamer loading no matter how high it was prior to breakout. However,
if you suppressed breakout (for wireless power transmission for
example), there might be merit to supercooling the secondary. Good
speculations - you are in very good company. Tesla went through similar
speculations 100 years ago. 

Safe coilin' to you, Erik!

-- Bert --