[Milsurplus] Fuses to protect transformers

[Richard Brunner]

Yes, inductance limits short circuit current.  Been there.  Another solution 
is to put fuses in the PRIMARY of the transformer.  This has two advantages: 
The fuse is in it's natural environment, low voltage and AC.  He may have to 
use slo-blow fuses to ride through the transformer inrush current.

Richard, AA1P


   I've nevefr heard of this approach being used to limit SC current in
> electronic equipment before but you can consider what the electric 
> utilities
> do to limit current through large distribution power transformers.
>
>     I work for our local electric utility company and we are working with 
> a
> large commercial customer that wants to connect a sizeable generator to 
> our
> network to power their much of their equipment load (using all of their
> generator output) and use our lines to supply the remainder.  Our 
> load-flow
> studies showed that our circuit breakers would become overdutied if a 
> fault
> were to occur on our lines while their generator was operating.  So we are
> going to install reactors (no, not that kind, but choke coils) in the
> secondaries of our substation's transformers feeding this customer's
> circuits.  The rapid rise in current during a fault will produce a
> high-impedance point at the chokes in the secondaries, thus limiting the 
> SC
> current and protecting the transformers.
>
>     You might try placing some amount of inductance (RF choke?) in the
> transformer secondaries.  I can't help you with an inductance value, but
> it's worht considering and researching.
>
>
> 73 de
> Gene Smar  AD3F
>