Re: Strange events and me coil unexplained

to: Paul

I bet you make the same mistake a lot of builders do --- your chokes were
located under your primary coil and not in a separate location with the HV
supply.  The primary induced a resonant current in the chokes with a value
many times the normal value, ie, induction heating in a sense, which melted
the wires.  If you use a choke place it with the power supply and not under
the primary, and also, to spoil the Q in this part of the circuit, use a
500 to 1000 Ohm, 25 to 50 watt power resistor in series with each HV lead,
or if using one end grounded, then in series with the HV lead.  Keep the RF
chokes small --- approx 50 turns ---- and then use the resistors to prevent
unwanted resonances.  Resonance can't occur if the resistance is beyond a
certain critical value.  If it does occur, as you discovered, it can easily
build to 30 to 40 times the normal supply current value and potentials can
build to 2 or 3 times the normal supply value.  Be sure to run a safety gap
in the power supply and this will become evident if you are hitting
unwanted resonances. 

The change in capacitance from inside to outside would explain the tap
change.  Inside you were effectively "seeing" more coil to structure
capacitance which required more inductance to bring the primary into proper
resonance with the sec coil.


> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Strange events and me coil unexplained
> Date: Wednesday, December 16, 1998 12:04 PM
> 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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