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Re: Calculating Sec. Voltage
At 12:26 AM 2/7/97 -0700, you wrote:
>Subscriber: Rodney.Davies-at-anu.edu.au Fri Feb 7 00:05:12 1997
>Date: Wed, 5 Feb 1997 23:38:14 +1100 (EST)
>From: Rodney Graham Davies <Rodney.Davies-at-anu.edu.au>
>To: tesla-at-pupman-dot-com
>Subject: Re: Calculating Sec. Voltage
>
>Hi Richard,
>
>On Tue, 4 Feb 1997, Tesla List wrote:
>> Rod,
>>
>> Not intending to be flipant, but ....3,555,555.556 volts!!!!!!
>>
>> Whew! Golly!
>
><grin>
>
>> In probably the most highly developed mathematical model imaginable, I think
>> there might be a bit of bauble about the first digit (3) in your answer,
>> much less the .556volt trailing figure!!!
>
>Being too technical again on my part I think...but no, it really is a
>3.5MV coil...claims to have been a measured value (by Questacon).
>It gets arc lengths to just over 4metres, no problem.
>
snip
>Looks to me as to get out the big-old voltage divider and hook it up to a
>voltmeter and let the Coil arc to it...even so, the results from the
>meter won't be constant...but will give you a good idea, hopefully.
>Margin of expected error +/- 200,000v.
>
>Thanks Richard, your comments have been very contructive and helpful.
>
>Cheers!
>
>Rod
>
>Rod,
If someone says they have ACTUALLY measured the voltage out of a big coil
like that, you better press them for the method of just how they did it, in
detail! If they really did a hands on measurement, it is most likely they
inferred or calculated the actual final voltage from some sort of field
measurement. (not necessarily a good method for any kind of reliable accuracy)
The voltage divider bit might work with a little 100KV coil, but at the
higher level, forget it. Where are you gonna' get resistors that won't arc
over at 4 meter arc levels!!! If the voltage is on the order of 2,000,000
volts, you wouldn't want to load the coil and so I would opt for a string
that would draw no more than 100 ua max! That's 10,000 ohms per volt. Thus
you would need a calibrated 20 billion ohm resistor, (2X10^11 ohm), over 15
feet long to set up the large drop inseries with maybe a 10 kilohm resistor.
The big resistor would need to be capable of handling at least a couple of
hundred watts.
Capacitive dividers might offer a much more doable form of divider. It
would still be a 5 meter long vacuum capacitor on the input end though.
This would avoid arcing. I have used the capacitive divider method on a
couple of my micro coil systems. (under 3" arcs) . The small coils must
always be retuned under load and the load must be well below 6pf total. The
results were way below the "pie in the sky" estimates above. The three inch
arc coil measured 28KV AC RF at 1.3mhz!!!! This can't be used as a guide as
in 9.333333333 KV per inch to extrapolate to larger systems unless you are
into serious self deception.
Who measured this 3.5mv voltage again!!!
Richard Hull, TCBOR