Re: Transformer question - over volting

    I have 2 voltage correction transformers. Theey are for 480 to 240 or
240 to 120. I'm run them in a conficuration atat gets 480 from 120v. In a
test I placed them in series in the 120 to 480 configuration and took the
480 from the first one to about 2000v without problem. The second
transformer didn't seem to mind at all and didn't pull loads of current. The
small 1.25A variac I tested with putting 244v on let out a lot of smoke and
the windings darkened, but it still works fine. I only ran 244v on it until
my bench about cought fire however :)
> Hi All,
>          recently there have been several posts about running 120V
> transformers or variacs off 240V and I would like to make a point here.
> A transformer can take a certain number of volts per turn at a give power
> level.  For different input voltages you wind a different number of
> turns.  If you over volt it the power input you are trying to put through
> core is way above what the core can take saturating the core, the
> core sinks a huge amount of power from the mains which completely destroys
> the primary windings and probably melts the secondary as well.
> A transformer can be run below its rated input voltage but *never* above
> more than 10% or so. If you do try to run a transformer above it rated
> voltage by much you are guaranteed to let the smoke free in big way.
> You can very easily and cheaply buy conversion auto transformers to step
> or down between 240V and 120V, If anyone in the UK needs one I have pair
> these rated at about 600VA which I will sell for about 10 each.  Most
> variacs also have a 120V and 240V tap to allow them to be used to step up
> down between these *and* provide variable voltage output at the same time.
> Keeping the smoke in in GB
> Nick Field