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*To*: tesla-at-pupman-dot-com*Subject*: RE: New formula for secondary resonant frequency*From*: "Tesla list" <tesla-at-pupman-dot-com>*Date*: Fri, 02 Feb 2001 20:12:53 -0700*Resent-Date*: Fri, 2 Feb 2001 20:16:00 -0700*Resent-From*: tesla-at-pupman-dot-com*Resent-Message-ID*: <OBwzs.A.iEC.qf3e6-at-poodle>*Resent-Sender*: tesla-request-at-pupman-dot-com

Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-uswest-dot-net>" <couturejh-at-worldnet.att-dot-net> Paul, All - I checked your new formula with the JHCTES Ver 3.2 on line computer program with the following results. The Ver 3.2 and the formula appear to agree closely with the first three coils but with Marc's coil there is a big discrepancy. The Ver 3.2 gives a much lower kHz (248.06) for this 1700 turn coil compared to the formula. This is strange because the Ver 3.2 as I recalled agreed closely with John Freau's coil of 1550 turns. John could you check this for us? I used 2.1 Rad, 1550 turns, 68 TPI, 0 for Sec term, with output 261.92 kHz. Marc could you run John's coil through your formula? Also thank you for giving me this opportunity to check the JHCTES program. Coil A B C D E Big CW 90.9 90.2 0.7 92.02 1.12 Half coil 150.7 151.4 0.7 150.58 0.28 Terry 148.4 146.1 2.3 150.58 1.73 Marc 276.9 276.9 0 248.06 28.84 John F. ? ? ? 261.92 ? A - Measured kHz B - Formula calc kHz C - Difference between measured and Formula D - JHCTES Ver 3.1 or 3.2 calc kHz E - Difference between measured and JHCTES Note that for the Half coil and Terry's coil the JHCTES is closer to the measured value than the formula. It would help if more coilers would measure their coils and check the results with the above two calc methods and advise the List. John Couture --------------------------- -----Original Message----- From: Tesla list [mailto:tesla-at-pupman-dot-com] Sent: Friday, February 02, 2001 7:06 AM To: tesla-at-pupman-dot-com Subject: New formula for secondary resonant frequency Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <paul-at-abelian.demon.co.uk> Hi All, Calculator fiends may like to try out the following formula for estimation of secondary resonant frequency. Applies to bare coils (ie no top-load and no primary) in normal grounded-base configuration, when situated over a reasonably well defined ground, with the coil base not more than half the coil length above ground. Starting with: turns; h = length of secondary winding, metres; d = diameter of secondary - metres; b = height of winding start above ground - metres; awg = wire gauge, AWG; (metres = inches * 0.0254) Compute: x = h/d (form factor) wd = 7.348e-3/pow(1.122932, awg-1) (wire diameter - metres) sr = turns * wd/h (spacing ratio) fa = -94.6683*awg*awg*awg + 9000.55*awg*awg - 301175*awg + 3.64056e+6 fs = 3.50662*sr*sr - 7.90171*sr + 5.83019 fx = -0.000211179*x*x*x + 0.00557568*x*x + 0.0664809*x - 0.0153254 t = fa * fs * fx/h/h s = -3.85188e-15*t*t*t + 1.17176e-8*t*t + 0.631829*t + 482.463 and finally, fb = log( b/h/0.2) (use the natural logarithm) Fres = s * (1.02 + fb/98.9065); (Hertz) Accuracy is around 2% average, with a peak error of around 4%. Some examples: My big CW coil: b=0.15, h=1.6, turns=725, awg=12, d=0.58; Measured 90.9 kHz, formula 90.2 kHz, -0.8% error My half-coil: b=0.15, h=0.8, turns=365, awg=12, d=0.58; Measured 150.7 kHz, formula 151.4 kHz, +0.5% error Terry's big coil: b=0.025, h=0.762, awg=24, d=0.2606, turns=1001; Measured 148.4 kHz, formula 146.1 kHz, -1.5% error Marc Metlicka's large h/d coil: b=0.3302, h=1.07696, awg=24, d=0.1081, turns=1700; Measured 276.9 kHz, formula 276.9 kHz, 0.0% error The formula was derived by curve fitting to a database of around 1700 simulated secondary coils, and is expected to be more accurate than estimates based on Medhurst capacitance. Regards, -- Paul Nicholson, Manchester, UK. --

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