[Milsurplus] Fuses to protect transformers

[Peter Gottlieb]

Inductance factors in fault current and arc flash studies. All large transformers have their measured impedance stamped on the nameplate. 


Peter

> On Mar 16, 2014, at 10:55 PM, "Richard Brunner" <brunneraa1p at comcast.net> wrote:
> 
> 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
> 
> ______________________________________________________________
> Milsurplus mailing list
> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Milsurplus at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html