Re: Need help with mystery

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

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: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<youngs-at-konnections-dot-net>

> Here is the puzzle.  My most recent power resistor is 6 400 ohm 10 watt
> power resistors in parallel for 67 ohms at 60 watts.  Current going the
> resistors is high amperage pulses, but the average current is only 50
> milliamps.  Current is measured with an ordinary moving coil ma meter.
> 
> Power dissapation for this series resistor is I-squared R = .05 x .05 x 67
> which is about 0.17 watt.  So the resistors will stay cold, right?  Wrong!!
> When the TC runs for a minute, the resistors get literally smoking hot!  I
> am guessing the power dissapated is well over 100 watts!!  This means the
> resistor impedance is at least 40K??
> 
> Another clue is that the voltage pulse across this power resistor is on the
> order of 5 KV as it will jump across a 1/4 inch gap.  If the power resistor
> is a pure resistor, this would indicate current pulses of about 75 amps
> flowing into the 19 nF tank cap.

The problem is that you are mixing RMS and average values. You are
really
charging the capacitor with pulses of 75 amperes, that make the RMS
current
on the resistors far larger than the average 50 mA that you measure.

Antonio Carlos M. de Queiroz