Re: [CAD_CAM_EDM_DRO] Transformer ???

In a message dated 1/18/2003 7:28:08 PM Central Standard Time,
godsone@... writes:

> Great , but is there any way to find out how many amps it can put out .
> What happens when I exceed that ( this thing is way too big to overheat)
> will it burn out the wire ?
>

Ron: Can you SEE the actual enamelled "magnet-wire" for each secondary (as
the ends come out to the solder-tag, say)? If you can "mike" that (with a
vernier caliper, etc.), there is a "wire table" in my Roll Your Own
Transformer article (see link below), that can help you guess the rated
current per winding. You can also "do some math" and determine the total VA
rating of this big job, and then figure if you are close in your
calculations, buy adding the total VA of all four windings. They ARE
separate, right? Check with an ohmmeter to see if any are "same, tapped
winding".

I can see ONE possibility you might try: See if the voltage you get by
connecting the 30 and 10 volt secondaries in series is very close to that of
the 40 volt winding. If so, parallel those two 40 volt windings (being sure
to "tape off" the joint between the 10 and 30!). That will ADD the current
of those two. ONE volt of difference would be insignificant. But if five or
more, it could cause some heating.

A shorted winding will cause overheating of the winding, at least "deep, down
in there", and ruin the whole transformer. If you exceed a current-demand
by, say, more than one amp per 750 circular mils for a given secondary, by
more than 20% for more than, oh, quarter hour for a 1 KV transformer, or more
than 50% for more than a minute or so, you will probably damage the
insulating materials "down in there", from the "enamel" (Formvar), to the
"paper and tape and stuff". SMELL is a good detector, as is just plain FEEL
of the iron core, but neither of those precision tests is sufficiently
instantaneous to be good "preventive testing". As a transformer is an
EXPENSIVE thing (material AND labort-intensive!), they should be respected!
Be careful!

<A HREF="http://members.tripod.com/~schematics/xform/xformer1.htm">Roll Your Own Power-Transformers!</A>

Jan Rowland



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