Re: Saturable Reactor

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>

MOTs seemed ideal because they're cheap, relatively
HV, and available.  The problem with common 240/480
three-phase transformers is that the windings are
going to have very low DC resistance, owing to
heavy-gauge windings and relatively few turns in those
windings.  These characteristics will mean that your
DC control will have to put out quite a bit of current
at a very low voltage, which is a little awkward.

I tried to locate a three-phase transformer having a
high voltage of 2400-4160V, which would tend to imply
a higher DC resistance on the HV winding, and
therefore a better chance of using one or more of the
HV windings for a control winding by simply hooking up
a recitified variac.  I did immediately locate a 3kVA
4160V-240V transformer on eBay, but the guy wanted
almost $500 for it!  By contrast, my local utility
offered me a 75kVA three-phase unit, 14.7kV-480/277V,
for $300 (they're nice to me :))  It was oil-filled
and weighed several tons.  Had to turn that one down,
though! (maybe someday I'll have the real estate to
play with something like that).

...but there's nothing magical about the MOT idea.
Pairs of identical pole transformers ought to work
nicely, too.  When talking about stuff like that,
however, I start to get pretty worried about what
might happen if one pig should fail.  In fact, even
with MOTs, I'd like to see some more research done
into how to make the MOT-based SR's safe.  Not pushing
them too hard certainly seems like a good idea!!

Regards,
Aaron, N7OE

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: Yurtle Turtle <yurtle_t@xxxxxxxxx>
>
> Most recent talk about SR's has been on MOT's, but I
> seem to remember someone mentioning a 3 ph. dry type
> distribution transformer, such as this one:
>
>
http://www.hot-streamer.com/adam/garage/transformer_30a_kVA.jpg
>
>
http://www.hot-streamer.com/adam/garage/transformer_30b_kVA.jpg
>
> Has any further work been done for something like
> this?
>
> thanks
> Adam
>
>
>