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Re: Strange events and me coil unexplained
Tesla List wrote:
>
> Original Poster: "Paul Marshall" <klugmann-at-hotmail-dot-com>
>
> Hey everyone,
> Last night I ran my 6.5" coil at approximatly 5 Kw. 14.4 Kv. My air
> choaks melted. They were wound with 18 AWG insulated wire. Even the PVC
> core melted and twisted. How is this possible, there should only be
> millamps on the HV side ? My capacitance has also increased. I made
> these caps over a year ago. Each cap is .026 uf. I have 4 in the
> circuit, two each in parallel and then these two circuits are in series.
> Ordinarly I'm taped out with the large top load at the 13 th. or 14th.
> turn. Last night I had to tap in to the 9th. turn ! A few weeks ago I
> move the coil outside and noticed that I had to tap in. I attributed
> this to ground clutter. Could the caps still be setteling ?
> The calculated value of these caps were .026 uf. They had a measured
> value of about .024 uf. They are poly plate caps. Does anyone have
> anyone have any ideas about the RF choaks or the the caps ?
>
> thanks,
> paul m
>
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Paul,
One other possibility - if you used bypass caps in addition to chokes in
your LC protection network, you may have been getting high frequency RF
heating in the chokes. Charged bypass caps (plus HV transformer winding
capacitance and the parasitic capacitance of your HV wiring) will be
disruptively discharged through the chokes whenever the main gap fires.
Without damping resistors, the resulting LC circuit can ring with
relatively high RF choke current (much higher than the average low
frequency charging current). Skin effect combined with the higher RF
current might be account for the heating you observed...
The tap changes are most likely caused by reduced capacitance from the
toroid and secondary to surrounding objects - higher inside (closer
conductive objects, electrical wiring, etc versus outside in free air).
The operating frequency of the secondary system rose, requiring you to
tap in to compensate.
-- Bert --