Concur. At 15 kV 120 ma, I'd consider 22 AWG magnet wire.
From: David Rieben <drieben@xxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sunday, February 22, 2015 6:22 PM
Subject: Re: [TCML] Dual identical FRANCE neon sign transformers (15000v 60mA each) in parallel
I'd think that 6" would be a pretty optimal secondary diameter for a ~2 kVA Tesla coil. If you can't find a sufficient length of it at Lowe's of Home Depot (try asking them if they have it or can get it, if you can't find it), I would try a local plumbing or irrigation supply. #26 AWG wire would be pushing the envelope in wire thinness for a coil this size, but it would work. And a 24" secondary winding length would be sufficient for this power level, assuming that you topped it with a properly sized toroid topload (~6"x 24"). You could probably get away with a 4" diameter coil, but 6" would be better and would likely give you longer sparks with a given amount of power throughput, compared to a 4" coil. So, in conclusion, I would aim for a 6" (or even 8") diameter by 24-26" winding length of about #24 AWG magnet wire (or 30" to 32" long for an 8" diameter form) for my finished secondary. If the PVC doesn't pan out, you can also use one of those cardboard
concrete former tubes. Lowe's and HD both carry these in 8" and 12" diameter by 48" long. The 4:1 to 5:1 is a good aspect range to aim for but it isn't really that critical, so long as you keep your dimensions within reason ( >3:1 and < 7:1 would probably be just fine). If you go the cardboard concrete former tube route, you'd just need to make sure that you completely evacuated any stray moisture from it (heat it or place it out in the sun for several hours on a warm, dry day) and then soak and coat it with several coats of polyurethane spar varnish (to keep moisture out), as cardboard is notorious for soaking in atmospheric moisture, especially in humid ambient conditions.
David
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