Re: MOT leakage

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

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi,

You may want to consider putting a thin sheet of copper in between the 
tranny and the steel.  That will soak the induced currents up first.

If all else fails.  Glue a 1/2 inch sheet of G-10 to the chassis and give 
it the  resonance of solid rock ;-))  Or weld on thick steel chunks as 
needed.  If you can simple turn the tranny 90 degrees, problem solved too!!!

Cheers,

         Terry


At 06:08 PM 11/8/2004, you wrote:
>Thanks for the reply.
>
>The reason I got this MOT was that it was larger than any others I have 
>come across, and I'm only drawing about two thirds of its rated power. 
>That's why putting two together seems overkill.
>
>What I want to ask is about shielding.  Someone suggested I put it in a 
>steel box filled with potting compound.  This should attenuate the leakage 
>to the outside and the compound should prevent the box from vibrating too 
>much.  Reinforcing the power supply chassis should deal with the remaining 
>hum.  However, I'm wondering if heat will dissipate well enough through 
>potting compound.  What sort of material is recommended, that is not too 
>hard to obtain (I'm also in Canada, which makes getting things like that 
>harder)?  Another thing is, I've noticed that most leakage seems to be 
>around the exposed parts of the windings rather than the core.  The 
>chassis buzzes least when the transformer is set in such a way that the 
>closest part to the chassis is an outer side of the core.  So what I'm 
>wondering is if it's OK to just shield  the sides of the transformer, so 
>there is better cooling.  I have seen many enclosed transformers that only 
>cover the windings, though perhaps that is more of a safety feature rather 
>than shielding (I'm referring to tube amp transformers which often are 
>mounted on top of the chassis).
>
>Another person suggested an aluminum chassis but I need the shielding of a 
>steel one.
>
>>It may get slightly quieter under load, as the IR drop in the primary will
>>reduce the maximum flux that the core sees. But to get a big improvement you
>>might have to build a new transformer with a larger core area or more
>>primary turns.
>>You might like to try "mating" the E parts of two identical MOTs together
>>and connecting the primaries and secondaries in series. This will give the
>>same output voltage but will half the peak flux density so it should run
>>much quieter and leak less flux.
>>Steve C.
>>