I can very well understand the temptation to use MOTs, since they are so
widely available for free, and let's face it, most of us are cheapskates!
But please do understand what MOTs are:
They are the absolutely cheapest possible implementation of a
current-regulating transformer, designed to work always at fixed full
power, for a few minutes at a time, in the airstream of a fan.
And for a ham linear amplifier you want:
- NOT a current regulating transformer, but one that is the exact
opposite: As stable a voltage as possible.
- A transformer that idles very well, since typically at least 80% of
the time a ham amp transformer will be idling.
- A transformer that can stay energized for the 48 hours of a contest
weekend, or the two weeks of a DXpedition.
So the requierements for a ham amp transformer are diametrally opposed
to those for a MOT, and it's just not very convenient to adapt MOTs for
ham amplifier use. Better use purpose made transformers for ham amps,
and leave the free surplus MOTs for other hobby applications to which
they are better suited, such as small spot welders to weld those battery
tabs, light effect setups using gas discharge tubes, Jacob's ladders to
scare away your mother-in-law, and the like.
It's perfectly possible to recover just the core of a MOT and rewind it
as a normal transformer with good efficiency, but this requires throwing
away the wire, which is the expensive part, to recover the iron, which
is rather inexpensive, and then do all the winding work. On top of that
many MOTs have the cores welded together, so they are damaged when taken
apart. And a 1500 watt MOT will only make roughly a 200 watt, normally
efficient transformer!
This is basically an option for people who can't buy transformer
laminations new. If you can buy them new, better do that, because the
laminations contained in a MOT would be worth only about 3 dollars! And
from a scrap yard, less than one dollar...
Manfred
========================
Visit my hobby homepage!
http://ludens.cl
========================
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|