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First coil questions: resonant charging primary & coil forms
I'm well along assembling materials for my first coil, and have 2 specific
questions before I start fabrication:
1. What are the benefits, drawbacks, and system requirements for
establishing "resonant charging" of the primary capacitor? Several posts
have alluded to performance gains when resonant charging at the 60 Hz AC
input frequency is attained, but how exactly is this accomplished? I will
be fabricating an oil-immersed flat-plate polyethylene-dielectric primary
capacitor with coiled-copper tube primary, so I will the ability to
configure both a specific capacitor value and primary inductance IF I KNOW
THE DESIRED VALUES. I have (2) 15 kV/60ma NST's, plus (1) 15kV/120ma NST to
mix and match for input power.
2. Relative to coil forms for winding the secondary, what are the REAL
issues with thin-wall PVC? The textbook RF dissipation factor for PVC is
high compared to other polymers, but does this really come into play in a
TC secondary? If the material is "lossy", where do the losses go besides
heat buildup in the coil form? Is the heat buildup significant over a 2-3
minute run time? Do multi-kilowatt systems using PVC coil forms get hot
enough from dissipation-induced heating to deform the PVC tube? Do the
frequently-recommended multiple coats of insulating varnish on the coil
form provide a seal against moisture absorption, provide a "standoff"
distance to separate the secondary winding from the PVC to reduce
dissipation losses, or ??? What are the extents of the RF field surrounding
the secondary wire (i.e. would additional separation from the surface of
the PVC significantly reduce dissipation losses within the PVC?).
Any comments are appreciated
Scott Hanson
Costa Mesa, CA