# Wire Insulation Thickness

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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.

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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

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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

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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

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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.

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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.

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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.

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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.

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What do you think?

Does this make sence?

Gary Weaver

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