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Wire Insulation Thickness
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From: Scott MacGregor [SMTP:smacgregor-at-aasp-dot-net]
Sent: Tuesday, May 26, 1998 11:14 PM
To: Tesla List
Subject: Re: Wire Insulation Thickness
Tesla List wrote:
>
> ----------
> 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 used a micrometer to check 2 lengths of enamel coated copper wire every
> 1". Then I removed the insulation and checked the diameter again. I was
> surprised that acetone would not remove the enamel coating. I heated the
> wire over a candle to burn off the insulation then cleaned off the carbon
> with 0000 steel wool.
>
> ----------------------------------------------------------------------------
>
> Here are the results for #20 enamel coated copper wire.
>
> A = Wire diameter with enamel coating on the wire.
> B = Wire diameter with enamel coating removed.
> C = Insulation thickness including both sides.
> D = Minimum insulation thickness of one side only.
>
> A B C D
>
> .0350 .0301 .0047
> .0348 .0301 .0047
> .0347 .0301 .0046
> .0348 .0301 .0047
> .0350 .0300 .0050
> .0345 .0301 .0044 .0022
> .0345 .0300 .0045
> .0345 .0301 .0044
> .0345 .0300 .0045
> .0345 .0300 .0045
>
> ----------------------------------------------------------------------------
>
> Here are the results for #24 enamel coated copper wire.
>
> A = Wire diameter with enamel coating on the wire.
> B = Wire diameter with enamel coating removed.
> C = Insulation thickness including both sides.
> D = Minimum insulation thickness of one side only.
>
> A B C D
>
> .0238 .0202 .0036
> .0240 .0202 .0038
> .0238 .0202 .0036
> .0235 .0202 .0033
> .0235 .0201 .0034
> .0235 .0201 .0034
> .0235 .0201 .0034
> .0235 .0201 .0034
> .0235 .0201 .0034
> .0232 .0201 .0031 .00155
>
> ----------------------------------------------------------------------------
>
> I measured the arc length on a 15K neon and it measures .812 maximum.
>
> 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.
>
> -----------------------------------------------------------------------------
>
> Minimum insulation thickness for #20 wire is .0022
>
> Minumum insulation thickness for #24 wire is .00155
>
> 2 wires wound on a coil side by side will have a insulation thickness double
> this figure.
>
> 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.
>
> ----------------------------------------------------------------------------
>
> 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.
>
> 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?
>
> Gary Weaver
Interesting idea. It would, of course, change the turns/inch ratio. This
in turn would lower the inductance. Wouldn't you now need even higher
primary voltage/current for the same output? Maybe, you'd be right back
to the same situation?!
--
Regards,
Scott MacGregor EES,Co.
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Enterprise Engineering Services Co.
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