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*To*: Tesla Coil Mailing List <tesla@xxxxxxxxxx>*Subject*: Re: [TCML] MOT Measurements*From*: bartb <bartb@xxxxxxxxxxxxxxxx>*Date*: Sun, 11 Jan 2009 12:55:41 -0800*Cc*:*Delivered-to*: teslaarchive@xxxxxxxxxx*Delivered-to*: tesla@xxxxxxxxxx*In-reply-to*: <004c01c97098$68ede1d0$99d961cb@LINNEYPC>*List-archive*: <http://www.pupman.com/pipermail/tesla>*List-help*: <mailto:tesla-request@www.pupman.com?subject=help>*List-id*: Tesla Coil Mailing List <tesla.www.pupman.com>*List-post*: <mailto:tesla@www.pupman.com>*List-subscribe*: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@www.pupman.com?subject=subscribe>*List-unsubscribe*: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@www.pupman.com?subject=unsubscribe>*References*: <496095F7.22612.41E20C@xxxxxxxxxxxxxxxxxxxxx> <004c01c97098$68ede1d0$99d961cb@LINNEYPC>*Reply-to*: Tesla Coil Mailing List <tesla@xxxxxxxxxx>*Sender*: tesla-bounces@xxxxxxxxxx*User-agent*: Thunderbird 2.0.0.19 (Windows/20081209)

Hi All,

Xc = 1/(2 * pi * F * C) = 1/(6.28 * 50 * 2.25uF) = 1414.7 ohms. Since Xc=Xl at resonance, L = Xl/(2 * pi * F) = 1414.7/(6.28 * 50 ) = 4.5H.

Here's a series of equations for predicting an accurate Cres: ------------------------------------------------------------ w = angular freq = 2 * pi * F = 377 Cres = 1/(w * XLleak) XLleak = w * Lleak Lleak = L2 * (1-k^2)

L2 = L1 * Lratio Lratio = turns ratio^2 turns ratio = Vout/Vin (open circuit with low voltage to L1) L1 = XL1/w XL1 = Vin/Ioc where Ioc is the open circuit current of L1.

Vin = 60.2V L1 primary current with secondary open = Ios = 0.43A L1 primary current with secondary shorted = Isc = 10.63A --------------------------------------------------------- For turns ratio: Vin = 10.14 and measured Vout = 182V --------------------------------------------------------- XL1 = L1 reactance = Vin/Ioc = 60.2 / 0.43 = 140 ohms L1 = L1 inductance = XL1/w = 140 / 377 = 0.37136H Turns Ratio = Vout/Vin = 182 / 10.14 = 18 Lratio = turns ratio^2 = 18^2 = 324 L2 = L2 inductance = L1 * Lratio = 0.3714 * 324 = 120.32H k = sqrt[1 - (Ioc/Isc)] = sqrt[1 - (0.43/10.63)] = 0.9796 Lleak = Leakage Inductance = L2 * (1-k^2) = 120.32 * (1-0.9796^2) = 4.859H XLleak = Leakage Reactance = w * Lleak = 377 * 4.859 = 1831.8 ohms Cres = 1/(w * XLleak) = 1/(377 * 1831.8) = 1.45uF I previously listed Cres at Vin, so let me use the above method and compare. Microsim Above method Vin Cres(uF) Cres(uF) ------ -------- -------- 10.14 1.39 1.39 20.00 1.34 1.35 30.20 1.37 1.36 40.20 1.32 1.35 50.10 1.35 1.38 60.20 1.47 1.45 70.20 1.57 1.57 80.00 1.72 1.70 90.10 2.20 2.18 100.00 2.34 2.37 110.10 2.68 2.68 120.20 2.83 2.93

Best regards, Bart tesla wrote:

Greetings again team, thanks all for comments on this interesting threadI had a practical look tonight into the resonance effects of a MOT . Ihad been assuming that the thread was concerned with finding out whatresonant rise would occur and at what capacitance of a single MOTwithout any primary ballasting in that cct.METHOD I used a normal 600 watt MOT with magnetic shunts in place.I incremented the secondary load by 150nF steps up to 2.475uF andmeasured the voltage across the secondary.The source driving the MOT was a large Variac i.e. a voltage sourceand a very low source impedance.The results were interesting.With sufficient primary excitation to cause over well 10 amps ofprimary current at resonance the resonance was very slippery changingwith excitation as saturation effects altered the inductance. It waspossible to find excitation values where you could watch the wholesystem "pull" into resonance slowly At lower excitation resonance wasstable and occurred at 2.25uF above that capacitance the voltagemagnification dropped off very quickly. I did not measure the primaryvoltage but it was quite low of the order of 60 volts. The voltmeterwas a digital panel meter version of Peter Terren's "High VoltageMeter" on his Tesla down-under site (a great site)Some of the data points were Load 0.6uF Secondary voltage out 398 Load 2.25uF Secondary voltage out 1352 (at or close to resonance) Load 2.4uF Secondary voltage out 513The inductance seen by these capacitors is thus 4.5Hy in thisconfiguration. Whether this is leakage L or transformed L from theprimary side by N^2 or all of the above it seems to me that is theinductance the practical external load has to deal with when decidingwhat capacitive load will actually cause resonance.Hope this is useful data, full data can be sent to anybody who wouldlike itBest Ted L in NZ _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla

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**Follow-Ups**:**Re: [TCML] MOT Measurements***From:*tesla

**Re: [TCML] MOT Measurements***From:*bartb

**References**:**[TCML] MOT Measurements***From:*Herwig Roscher

**Re: [TCML] MOT Measurements***From:*tesla

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