Re: MOT power supply

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 01:19 PM 11/19/2002 -0700, you wrote:
>Original poster: "tesla by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><tesla-at-paradise-dot-net.nz>
>
> >Thanks for this data Finn this is ther very first time I have seen a real
>rating for core to winding for a MOT.
>
>Still this figure is in air so in oil I'd imagine the stresses of a 4 or 6
>pak could be indefinate. My oil as I recall is rated at 70kv/mm


That 700 kv/cm is the rating with dry oil no contaminants, etc.   I assume 
that you probably don't scrub your MOTs, degas, dewater, decrud, etc. them, 
so the minute you put that MOT into the oil, you've introduced some 
contaminants.
However, a 3:1 ratio for oil/air  (i.e. around 200 kV/cm for oil ) is 
probably a nice safe ratio that is pretty oil quality independent.

You'd also need to look at the transformer design to see if the major 
dielectric contributor between wire and core is air(oil) or something like 
the wire insulation, the kraft paper, or a winding bobbin.

In all, empiricism is the best test. Plunge them in the oil and try it.



>Whatever the limits are I think good design with 6 paks in oil does not pose
>a problem from my own experience and judging from reports on the list.
>
>Hate to think of the ratio of dead NST's to MOT's or worse $NSTdead/$MOTdead
>Best to all
>Ted L in NZ
> > Typical insulation from winding to the core in a MOT is 7.5kV for 1
> > minute. It is only a question of how long they last.
> > This may well be adequate for coiling, and I encourage your attempts to
> > find the limit.