Re: current rating of transformers

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Andy Wander <awander@v...>
wrote:

> Yeah, but....
>
> I still say that the thing that limits the secondary current is the

wire

> gauge used for the secondary winding.
>
> I don't think many transformers are built using wire that's a lot

heavier

> than needing fro rated output current. Therefore, dropping the

primary

> voltage(thereby dropping the secondary voltage) doesn't mean you

can now

> pump more current through it to "get back" up to the VA rating.
>
> Andy Wander
> Verrex Corporation
>

Hi Andy,

You are exactly correct in that the wires in a tranformer are exactly
the correct size for the maximum of the transformer.

But heat the real limiting factor. too small a wire, and they
overheat and short out.

The transformer houses pay engineers to design these things and not
add extra copper for the fun of it. Imagine the cost of adding a
useless extra pound per transformer.


But, as Jon had said, you can connect these things for maximum power
or what much reduced power you need.

Since I'm looking at a 21 amp 48 volt supply, that could be a single
48 volt transformer.

As was said, if I am lighing 24 volt DC lignts on a 2 diode
rectifier, then the transformer will only send power at 1/2 cycles
and run much cooler.

In this case, the transformers I am looking into are listed as having
a higher rating with a choke input filter than with a capacitor one.

What I am learning from this thread is that transformers are not
always selected without design calculations.

Darn, life was so much easier when I thought I knew everything but
really knew very little.

Dave