Reduced-current MOTs and non-linearity

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jolyon Vater Cox by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>


In the course of investigating whether a MOT could be "tamed" to give a 
safer, more NST-like performance at lower current I conducted an experiment 
where a capacitor was connected in series with the primary of the MOT. The 
apparatus was comprised of 30-0-30 volt 2 Amp transformer,a 6 uF 250VAC 
motor run capacitor, a MOT and a multimeter. The following finding was 
interesting.

With the heater winding short-circuited and the MOT and capacitor connected 
to 60 volts AC

the voltage across the capacitor was 99 volts and the voltage across the 
primary of the MOT was 136 volts

When the same assembly was connected to 30 volts AC the voltage across the 
cap was 44 volts and the voltage across the MOT primary was only 22 volts.

By Lenz's law the secondary flux opposes the primary flux so that in order 
to keep the flux in the transformer core constant when a current is drawn 
from the secondary, the primary current MUST increase.

this is the behavior expected of a normal voltage transformer

but a MOT is partially current limited by virtue of the magnetic shunts 
inserted between the primary and secondary windings

so as secondary current increases the resultant opposing flux must "divert" 
some of the primary flux away from the secondary windings by forcing it to 
flow through the magnetic shunts instead

increasing the leakage inductance at higher voltages

so that the combination of the capacitor and inductor become more "in tune" 
with frequency of the mains supply when the voltage is increased.

Is this the cause of the non-linearity observed when the MOT and capacitor 
are connected to AC supplies of different voltage?

(Incidentally, the maximum current that could be drawn from the secondary 
when it was shorted with the milliamps range on the multimeter was 15mA 
with the assembly above).