Re: Transformer for Sale? POTENTIAL TRANSFORMER

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 4/17/03 1:31:33 PM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

>Sorry about the stupid question, but I'm just curious about one thing. How
>is it that you can push these things over their ratings? Is it simply that
>they aren't current limited and you can set their ballast to run at over
>their ratings? Will they draw more than their ratings naturally? Sorry, I
>guess I'm still used to living in "NST land" =D


Yes, a typical transformer that is not current limited will always
draw more than its rating when the load is heavy enough.  Thus,
external current limiting is normally used in a TC application.  The
rating is basically a temperature rating which says that the
transformer can run safely at that rating for a certain amount of
time without getting too hot.  In a potential transformer, a rating is
given which guarantees that the step-down accuracy rating will
be met.  If the transformer is overloaded, it will eventually heat up
more than usual, and the losses will be somewhat higher
too.  NSTs and other current limited transformers have shunt
reactances which limit the current.  NSTs and other current
limited transformers can sometimes supply more than their
rated current also, if the supply voltage is higher than normal,
or if certain capacitor values and break-rates are used.

John