Re: [TCML] MOT Measurements

[tesla <tesla@xxxxxxxxxxxxxxx>]

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.

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 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

Best
Ted L in NZ 

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