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Re: MOT to NST "extra transformer"
Hi Terry,
Running with 2kV on the primary will necessitate a lot of
primary inductance:
> Original Poster: Terry Fritz <terryf-at-verinet-dot-com>
>
> Hi All,
> I am going to get a MOT to play with and a thought occurred to me
today.
>
> Most MOTs (microwave oven transformers) put out about 2000 volts at 300 mA.
> The voltage is too low and current too high for most TC applications.
> However, how hard would it be to make a transformer to bring it to a nice
> level? Perhaps a 2000V/300mA primary and a 12000V/50mA secondary. Since
> the turns ratio would only be six to one, there should be room to use
> insulated 24 gauge wire on the secondary which would make it almost burnout
> proof (in oil). In fact, two or more MOTs could be used to drive this
> "extra transformer". The current protection in the original MOT should
> function normally (I think).
> Since the number of secondary turns is much less than say a 120v to
15000v
> transformer, such an extra transformer would be much easier for the average
> person to wind. With 24 gauge insulated wire in oil with poly between
> layers, It would be burnout proof no matter how hard it was hit. It would
> still need to be rated for 900VA and one would have to do a little design
> work but this may solve the problem of not being able to get HV
> transformers in certain countries and all that.
>
> Comments?
>
> Terry Fritz
and as the core gets smaller, the inductance must rise to keep Imag
from saturating the core. I don't think you'll be much better off
sizewise. Equations worth noting:
Magnetizing force = Np*Imag
Imag = Vp/2*PI*Fmains*Lp
Lp = k*Np^2 where k is a core induction constant
If Np halves, Lp quarters and Imag doubles. Nub of the problem is
that the core can only support so many Ampere-turns before it
saturates. For good transformer operation the core must be ungapped
so core area becomes a critical factor (flux density or flux/area^2)
Effective core length does not greatly influence maximum core flux in
an ungapped design and really only exists to allow a winding window
which in turn allows copper mass for a power rating.
Malcolm