Oil-immersed RFCs

From: 	Felix[SMTP:73374.1547-at-CompuServe.COM]
Sent: 	Sunday, August 31, 1997 2:15 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Oil-immersed RFCs

In your RFCs, is the number of 'slices' of winding driven much more by 
breakdown voltage than by inductance requirements? I've been looking at
 solenoid formulas and wire tables and offer this line of thought:
     Using no. 22 wire, which gave about 35 tpi on my Tesla secondary, one of
your slices of winding would have about 35 layers in its 1-in radial depth.
Postulating a two-slice RFC facing 60 kv spikes, we get roughly 1 kv per 
layer of winding or, as you point out, 2 kv between the ends of adjacent 
layers---or easily 5 kv if the layers are not laid down absolutely evenly
and some wires slip down into a lower layer
  Now 2 to 5 kv sounds to me like a lot for the few mils of enamel on my no.
 22 Phelps-Dodge Thermaleze, although I know volts/mil are higher for 
insulation in thin layers.
   This suggests that the choice of RFC wire gauge may be more critical than
it looks at first sight. I've never seen data on breakdown voltage of
enameled wires in the 22 to 28 ga region, far less at the high frequencies
of interest, but if for instance the insulation breakdown were about the
same over this range of wire gauges, then the thinner wire would be 
better due to fewer volts per layer.
I also notice that Tesla secondaries with 500 to 1000 turns and several feet
 of arc evidently achieve turn-to-turn breakdowns of 0.5 kv or more, and in 
the literature I haven't seen any concern about needing heavier secondary 
wire at higher arc length. This suggests that for our RFCs, something around
 1 kv between any two adjacent wires may be OK. This would call for dividing 
the total inductance of each RFC into about two to five 'slices', depending 
on how precisely your electric drill technique can place and separate the 
layers. As a by-product it would also give the several millihenries that some
 coilers favor.
How does all this sound to you?
The fun thing about coiling is that the circuit diagram can be so simple in
appearance, yet conceal so many unexpected subtleties.
    Regards, Felix