|[AMRadio] BC610 110v using one leg of 2207|
k4kyv at hotmail.com
Mon Nov 6 00:11:10 EST 2006
>From: "Jim candela" <jcandela at prodigy.net>
>I am talking about a simple auto-transformer to transform 220 down to 110
>vac. Using this method you can pull power from both HOT legs of your 220,
>and not worry about whether that 3rd wire is a ground or neutral, or what
>gauge wire that wire is.
Some 3-wire cable designed for 220 volts only has a smaller neutral wire
than the 2 hot wires. If you are going to pull 110 off the neutral and one
hot, you need to be sure that the 3 conductors are the same gauge.
Otherwise, the voltage will sag under load on one side of the line while the
voltage will increase on the opposite side. This could damage certain
equipment and could even be a safety hazard. Also, make sure the 3rd wire
really is a neutral, not just a safety ground. The safety ground might not
be wired directly to the neutral wire at the fuse box with a connection
designed to pull the same current as the hot wires.
I have a large 220-110v stepdown Sola transformer, and it gives better
regulation out to the exterior shack, than using one of the 110 volt
circuits directly. It also provides some isolation against rf crud on the
line. However, I am not presently using it.
One problem I have with this method is leaving the tranformer in line
unattended all the time. It could become a fire hazard in the event one of
the windings in the transformer develops shorted turns, or the transformer
is zapped with lightning. I have seen the major mess that resulted from a
power transformer burn-out in a tube-type stereo amplifier that happened to
be left on all night. I could imagine what would have happened if that had
been a multi-kva transformer instead of a small power transformer.
Maybe the transformer could be mounted in a fire-proof case or metal rack
away from flammable material, but there would still be the possibility of
smoke damage from burnt tar and paper inside the transformer. Transformers,
even hermetically sealed ones, will often produce a lot of smoke before the
fuse blows (if there is one).
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