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Re: Re[2]: Terry filter

Original poster: Gregory Hunter <tesla_39560@xxxxxxxxx>

It is a simple formula: the voltage (E) across a
resistor (R) is equal to the product of the resistance
times the current(I) through the resistor (E = I x R).

Suppose you applied the output of a 15kv/60ma NST
across a 1000 ohm resistor. 1000 ohms x .060 Amps =
60v. Even though the NST can produce a potential of up
to 15kvac, the 1000 ohm resistor will never "feel"
more than 60vac. 15kvac is what the NST can produce
when open-circuit. Across a non-reactive load, the
voltage will decrease as the resistance decreases. The
most extreme example is if you simply short the two HV
leads together. At zero ohms, the voltage will drop to
zero and the current will self-limit to 60ma.

This is very similar to how an NST works when it is
connected to a neon sign. When a neon sign is first
switched on, the neon fill gas is essentially an open
and the NST voltage quickly spikes to 15kvac. However,
as the high potential ionizes the neon, it gives off a
pretty glow, and its resistance quickly breaks down.
The voltage across the lamp falls to about 800v. This
is sufficient to maintain the 60ma conduction once it
has gotten started. From then on, the NST behaves more
like a ballast than a high voltage power supply. The
NST is really just a self-starting luminous tube

Does that help any?


--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: Sebastiaan Draaisma
> <sebas@xxxxxxxxxxxxxxxx>
> Chiang Mai, Monday, March 7, 2005
> In reply to: Terry filter
> Posted by:
> Posted on: Monday, March 7, 2005
> Hello Terry,
> Please forgive my lack of knowledge, but I don't
> understand it.
> Why would the voltage across the resistors be 120V
> if my NST provides 15KV?
> The resistors I would like to buy have the following
> specs.
> Power rating at 25 deg. celcius 280W
> Overload power rating 10x power for 5 sec.
> Resistance 5%
> Limmiting element voltage 2000Vrms
> Temperature coefficient 75ppm/deg. celcius
> Operating temperature -55 to +450 deg. celcius
> Best regards,
> Sebastiaan Draaisma
> Tesla> Original poster: Terry Fritz
> <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
> Tesla> Hi,
> Tesla> Assuming your transformer puts out 120mA, the
> voltage across the
> resistors
> Tesla> will be 120VAC which is well within their
> ratings. For 100W at 1000
> ohms
> Tesla> the RMS voltage is 316V at 0.316 amps. Under
> certain conditions it
> may see
> Tesla> voltage spikes into the thousands of volts,
> but the long ceramic coated
> Tesla> windings can take that fairly easily.
> Tesla> Cheers,
> Tesla> Terry
> Tesla> At 02:15 AM 3/7/2005, you wrote:
> >>Chiang Mai, den 7 mars 2005
> >>Hello Everyone,
> >>Can someone tell me if the voltage rating of the
> resistors in Terry's
> >>filter have to be equal to the peak voltage of my
> transformer?
> >>If not, why?
> >>Best regards,
> >>Sebastiaan Draaisma