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Re: [TCML] MOT Measurements

Greetings again team, thanks all for comments on this interesting thread

I had a practical look tonight into the resonance effects of a MOT . I had been assuming that the thread was concerned with finding out what resonant rise would occur and at what capacitance of a single MOT without any primary ballasting in that cct.

I used a normal 600 watt MOT with magnetic shunts in place.
I incremented the secondary load by 150nF steps up to 2.475uF and measured the voltage across the secondary. The source driving the MOT was a large Variac i.e. a voltage source and a very low source impedance.

The results were interesting.

With sufficient primary excitation to cause over well 10 amps of primary current at resonance the resonance was very slippery changing with excitation as saturation effects altered the inductance. It was possible to find excitation values where you could watch the whole system "pull" into resonance slowly At lower excitation resonance was stable and occurred at 2.25uF above that capacitance the voltage magnification dropped off very quickly. I did not measure the primary voltage but it was quite low of the order of 60 volts. The voltmeter was a digital panel meter version of Peter Terren's "High Voltage Meter" 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 513

The inductance seen by these capacitors is thus 4.5Hy in this configuration. Whether this is leakage L or transformed L from the primary side by N^2 or all of the above it seems to me that is the inductance the practical external load has to deal with when deciding what capacitive load will actually cause resonance.

Hope this is useful data, full data can be sent to anybody who would like it

Ted L in NZ
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