Wire Insulation Thickness

From:  Malcolm Watts [SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent:  Monday, May 25, 1998 11:42 PM
To:  Tesla List
Subject:  Re: Wire Insulation Thickness

Hi Gary,

> From:  gweaver [SMTP:gweaver-at-earthlink-dot-net]
> Sent:  Monday, May 25, 1998 4:37 AM
> To:  Tesla-at-pupman-dot-com
> Subject:  Wire Insulation Thickness
> I don't think the insulation on enamel coated copper wire is good enough for
> very high powered Tesla Coils.


> I measured the arc length on a 15K neon and it measures .812 maximum.

What type of electrodes?
> That equals 18,460. volts per inch.
> 1" = 18.46 KV
> 10" = 184.6 KV
> 100" = 1.846 MV
> ----------------------------------------------------------------------------
> The rule of thumb is about 1000 turns of wire on a secondary coil.
> A coil with 1000 turns of enamel coated copper wire will have the follow
> volts per turn based on the different length discharge sparks.
> 10" discharge spark = 184.6 KV =184.6 volts per turn.
> 50" discharge spark = 923 KV = 923 volts per turn.
> 100" discharge spark = 1.846 MV = 1846 volts per turn.
> 150" discharge spark = 2.769 MV = 2769 volts per turn.

I think those figures are way off beam. For one thing you have to 
explain why the coil doesn't flashover from top to bottom. I don't 
buy the E-field argument for a second. I can make resonators 
flashover top to bottom in sshot mode with a realistic amount of E 
in the primary. In repetitive operation, the sparks stretch way 
beyond those in sshot mode but there is no way Vout can be higher in 
one mode than the other. The other thing is you have to explain how 
you can exceed the old 0.5CV^2 limit.

> I don't know the exact voltage rating for enamel insulation but I bet its
> not high enough to hold up to 2769 volts or 1846 volts or even 923 volts.

It most certainly is. I have tested 0.9mm dia polyesterimide magnet 
wire to in excess of 9kVDC.

> ----------------------------------------------------------------------------
> This probably explaines why my 6" coil that produces 54" discharge sparks on
> 1350 watts has 11 burn spots on it between the turns.  Thats 996 volts per
> turn on the secondary coil.

One thing that is not at all obvious and that must be viewed in 
extremely dark conditions (sshot agin) are graceful arcs of corona 
stretching down the windings. Last year, I saw the most amazing sight 
in a well darkened room when I did this. I ran a 6" coil with a 9" 
shpere on top sshot and was stunned to see a *ball* of corona over 2' 
in diameter right around the top terminal.

> My 10" coil that produced 126" discharge sparks shorted out and caught on
> fire. That was 2325.9 volts per turn on that coil.
> None of my 4" coils have burn spots on them.  The largest one produces  24"
> discharge sparks from 750 watts.  Thats 443 volts per turn on the secondary
> coil.
> ----------------------------------------------------------------------------
> I was thinking it might be a good idea to wind a plastic fishing line
> between the wires on a large coil to increase the insulation rating.  The
> extra spacing should help arcing between turns.
> -----------------------------------------------------------------------------
> What do you think?
> Does this make sence?

I have my doubts.