Re: oil dielectric

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Xyme3-at-aol-dot-com>


In a message dated 5/14/2002 1:16:24 PM, tesla-at-pupman-dot-com writes:

<<  The oil actually keeps the coil cool by damping molecular

> movement.


    Having done some thermal design & studied transformer
    design, I'd find that surprising. 

The molecular movement he is referring to is particle bombardment. If the 
coil was in a partial vaccum it would quickly disintergrate. In air, the 
movement is retarded by the presence of other air molecules. 

 Oil, in a conventional
    transformer functions in two ways:
        Electrical Insulation
        Thermal

You are certainly correct, non moveing oil is a good insulator. 
Moveing oil would absorbe heat. In a large container, convection
currents would occur in the oil heated from the
eddy currents you mention below. I also agree that 
    The thermal effect is by being heated by hot spots
    (core eddy currents, coil resistance losses), then flowing,
    by natural convection, or, less commonly, pumped
    circulation, to a cooler spot where it can dump heat.
    Sometimes the cool spot is aided by heat sinks ('fins').
    cf any text on transformer design.

> The way I wound the coil was to wind it on a 3.5" OD
> PVC pipe and then slide a 4.5" OD PVC pipe over it and seal

    This makes me nervous.

> both ends.  I left a quarter inch hole in the top plug and used

> something like a turkey baster to fill the coil with oil. When I

> was done, I sealed the small hole.

    I say nervous because a sealed container, can, if heated,
    even by a fault, 'rapidly disassemble':  Explode.
    Unlikely, probably, here, but possible.  (Power
    transformers can and have exploded, when not vented.)

 
> I like this coil so much I'm going to wind another one.  This time

>I'll use finer wire if I can get some.
 >>