Re: Quarter Wavelength Frequency

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

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 


Ed:

The wire was .043 inch dia. which yields 1,698 turns.

78.15 in circumference x 1,698 turns = 11,058 ft.

1/4 lamda freq = 23 kHz w/o large toroid topload

With topload and 1 pF/ft of spark the Fres drops to 14.4 kHz.

Sec inductance was 530 mH (calculated but not yet measured)  We plan on
sitting it upright on Monday and taking the Fres measurement, DC resistance,
and inductance checks.

The Big Bruiser will be running strong for the Sept. 4th show.  Essentially
this is a large "magnet wire" type coil running with 0.3 uF cap at 22 kVA.
It should work fine if we can keep the "bugs" off the sec winding between
shots!!

Dr. Resonance

 >
 > Easy enough to do.  As a result of calculations of your big coil I
 > decided to modify the program to use a more accurate calculation for
 > inductance, which changes the results very slightly.  The result is that
 > I now get these outputs:
 >
 > Wire length 11058 feet
 >
 > Wire weight 56.07 pounds
 >
 > DC resistance 70.6 ohms
 >
 > Fr 16.779 kHz
 >
 > Inductance 522.11 MILLIHENRIES  (half a Henry, that's a lot!)
 >
 > Apparent precision not a bit warranted, of course.... This is for #18
 > wire, the largest for which the net winding factor came out to be less
 > than 1 so my program would allow the calculation.  B e interesting to
 > see how some of those extra parameters compare to what you've measured.
 >
 > For the record, I've found that calculating the number of turns from an
 > accurate value of RDC works surprisingly well, considering the probable
 > variations in R/ft for different lots of wire, and for the effects of
 > wire stretching for smaller sizes.
 >
 > Ed
 >
 >
 >