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Re: [TCML] Primary selfC



Dr.R, all


It's very low because this is only isotropic capacitance.  A normal
capacitor has two plates and this is similar to a single plate capacitor
with the second plate being ambient ground.  I would suspect it's only 3-4
pF if even that high.

I think I agree with that.. capacitor plates having a "positive" and "negative" connection.. however, for a primary coil, there is not this arrangement. The "plate" is literaturally connected as a short circuit across the applied voltage... It is not like it is if your cap has 100V between each plate, as there will only be a per turn voltage for a start, which voltage between turns has to be like 75% smaller (4 turns ?) . I think another chap went into this a bit more yesterday...

For a total of 600square inches, that would have to be 300 per sheet which would be 2 plates... 150 for 4 plates... 1.26nF.. so for a normal cap that would be the figure... but as we do not have this connection then I will assume ( just for today ) that there is a 75% capacitance drop per turn as it is in effect shorted out... its probably a lot more than that, though even so the max ballpark figure is going to be something like 600pF ? That's assuming a 1mm gap so if there is going to be even 5mm of gap then the capacitance is probably not even going to be worth considering...




I never use ribbon due to corona. Take a 5 sec B&W 400 ASA exposure and you will see what I mean. I did with earlier coils and the photos almost scared
me.  High level of degradation on the sec coil.  Perhaps for occassional
operation it's ok, but I would not make a commercial unit with sharp edged
ribbon.  Corona much less for copper tubing.



I know a lot of people say that, its a fair point, though in this case I am using less than 1,000volts so its not much of an issue...

Chris




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