RE: Why do primaries get hot?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>


Antonio -

You say average current is zero. How did you find the average current for a
100 amp (square wave?) pulse lasting 10 us at each 10 ms (100 pulses per
second) is 0.1 amps and the RMS current is 10 amps.

I get (100 amps x .00001 secs) = .001 amp sec for each pulse
and   (.001 x 100 pulses) = 0.1 amps for the RMS current.

John Couture

------------------------------


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Friday, March 01, 2002 9:01 PM
To: tesla-at-pupman-dot-com
Subject: Re: Why do primaries get hot?


Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
>
> Original poster: "Gregory Hunter by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>
>
> Dear List,
>
> Why do primary coils get warm? I'm aware of the insane
> current pulses, but they are of only a few uSec
> duration. The Cu tube coil should integrate the
> various currents with respect to time, like a heater
> element, thereby arriving at the average current. The
> average power supply current of even a monster Tesla
> coil is under an amp. 1/4" or 3/8" Cu tube should be
> able to carry a few 100ma all day without warming up.
> Is it RF heating?

The wire is not heated by the average current (that is zero,
by the way), but by the RMS current, that is much higher.
A 100 A pulse lasting for 10 us at each 10 ms has an average
value of 0.1 A, but an RMS value of 10 A.

Antonio Carlos M. de Queiroz