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Re: Primary coil configuration
Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>
Tesla list wrote:
Original poster: "Chris Farmer" <cfarmer@xxxxxxxxxxxxxxx>
Hi All,
I'm in the process of designing my first coil. I'm a junior in
EE and it just caught my intrest while I was researching HV
transmission lines. I have a 15kV 60mA NST and I'm reading as much
as I can about the rest of the design before I actually buy/build anything.
My question is what is the difference between making the primary
wind outward away from the secondary opposed to winding vertically
keeping the windings all the same distance from the
secondary. Also what does primary placement around the secondary
effect. If I move the primary up to the middle of the secondary
what will that effect?
Two differences:
Coupling coefficient between the coils. You need something around 0.1.
This is easily obtained with a flat spiral primary. A solenoidal
primary would use more wire for this same coupling.
Clearance between the coils, to avoid sparks between them. A flat
primary puts the primary as far as possible. A solenoidal primary is
an invitation for sparking between the top turn and the secondary
coil, and the field distortion may cause sparking along the secondary
coil too ("racing sparks", caused by excessive proximity between the
coils, and maybe excessive coupling).
A primary in the middle obviously reduces the maximum voltage that
the terminal can reach before sparking to the primary.
Antonio Carlos M. de Queiroz