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Re: UK coilers ? + stuff (fwd)
---------- Forwarded message ----------
Date: Sun, 2 Aug 1998 13:12:12 +0100
From: "chris.swinson" <chris.swinson-at-zetnet.co.uk>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: UK coilers ? + stuff (fwd)
Hi,
Thanks for your last mail :-)
I have a few other little questions on your last mail....
>>I haven't built a large coil, mine is only a 240 watter. I can get up
>>to 9" sparks off my coil. Has anyone built a 240 watt coil and got
>>bigger sparks than that ?
>
>Yes, using a 230 watt OBIT (Oil Burner Ignition Transformer), 10KV -at- 23
>ma., I got better than 36" sparks off the top torrid.
>
How did you manage this? People I know need a input of 12Kv -at-100 ma to get
this length. Were you running at 50Hz mains input or was it linked to a DC
driver of some kind ?
>
>No, generally speaking you want as high a primary voltage as you can to
>yield a higher secondary output voltage, BUT ther is a limit of about
>15KV above this voltage the coronal losses get too high and you get
>deminishing returns.
>
>>I know that the cap and spark gap would not be needed as the transistors
>would have to >switch to about 600Khz anyway. As far as I can tell this
>would work better and the coil >should run a lot smoother, Any thoughts
>any one ? ?
>
>You would still need good capacitors, it is fundamental to the operation
>of a Tesla coil!
The way I see it, the capacitor charges at the resonant frequency, but if
the transistor driver was already at that frequency I wouldn't have thought
you'd need the cap.
>
>>According to my secondary inductance calculations my coil is about 39
>>mH, But actual measurement shows 7.4mH. Does anyone know is this
>reduction
>>in inductance is good ? As far as I see it , it is but as far as I can
>>see it may increase capacitance which is bad.
>
>Actually you want the secondary's inductance as high as you can get it
>and you want the secondary distributed capacitance as small as possible
>for maximum secondary output.
>
>>Oh, I varnished my coil so that's why it's different.
>
>Varnishing the coil may increase it's distributed capacitance but it
>won't do have any
>effect what so ever on the coils inductance!
>
I know it will raise the capacitance of the coil a fair bit, though
according to the inductance calculation my coil should have been about 39mH
but it was infact 7.4. My only conclusion to this was due to the varnish on
the coil. My calculations are correct as other get the same results but
they don't match by far.
>
>>what's the output current of a coil ? I know the capacitor may well
>>give a very small peek of up to 1000's of amps, But the current rating
>of the
>>wire in my secondary is about 140 ma, Does this mean I can only draw
>>140ma or is there something else to it all.
>
>Typically the current output of a coil like yours is in the micro-amp
>range.
>The current out put is in accordance with the conservation of energy
>rule. ie the power input is the same as the power output (minus losses of
>course) so since the voltage output is soo much higher than the voltage
>input the output current must be accordingly much smaller.
>
I'm confused now. I can get a "electrical flame" off a TV flyback
transfomer. It ran at about 25Khz at 25Kv. The current of the secondary
would only be about 1ma. I later tried the same experiment with a car
ignition coil, Same specs ( kind of ) but the secondary current was a lot
higher. I did not manage to get a bigger "flame" but I did get bigger
sparks. I may be wrong but by these results.... More current=bigger sparks,
but, lower current = no sparks but a big "flame" off the coil.
A tesla coil runs at a higher frequency, a higher voltage so it should work
better but it doesn't. So I concluded that the current off the tesla coil
was far to high.