Re: [TCML] NST Measurements

[Ed Phillips <evp@xxxxxxxxxxx>]

The reason of core saturation is correct. But more specifically, it is 
the permeability that is changing due to saturation and this is what 
causes the inductance to change. Current through the windings, the emf 
due to current, and how much it permeates the core causes the 
permeability of the core to change. Change in inductance occurs because 
the winding and core permeabilities are magnetically linked when current 
is flowing.

Does that answer the question?
Bart"

   A quibble perhaps but it would be more correct to say that the 
inductance is changing because the permeability increases with the flux 
density at low input voltage levels which are far from saturation.  At 
the "correct voltage" the leakage reactance resonates with the external 
capacitance and THEN the core goes into saturation [if the insulation 
can take the voltage].  I have a 15 kV, 60 mA NST here which, with an 
0.006 ufd HV mica capacitor across the secondary, exhibits that effect 
at around 30 volts on the primary.  Blew up the HV scale on my Simpson 
meter in finding it out many years ago.  With the meter on the 5000 volt 
scale I was increasing the variac and boom.......  Last time I operated 
a loaded NST without a safety gap.  Transformer and capacitor survived 
OK but blew out the multiplier resistor on the meter.

Ed

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