Re: A Bridge Replacement A Good Idea?

Pooh Bear wrote: 
John Popelish wrote:


No fuse will save the rectifier though. A fuse is there to stop fires. 

There are certainly fuses designed to do exactly that.  They are
called rectifier fuses or semiconductor protection fuses.



I should have said no 'normal' fuse like I did in an earlier post ! Mea culpa.



For instance:
http://www.ferrazshawmut.com/oem/resources/literature/HiSpdGuide.pdf

I'm not saying this one is intended to protect these diodes, but that
it will do it anyway for any normal operation of this circuit.  After
1 or 2 other component failures, all bets are off as to what's left
after the fuse blows.



FF fuses are horribly expensive. Easier and likely cheaper to put in a beefier part if
available.

In the end though - fuses are simply there to stop the equipment cable burning.

Evidently you don't deal with equipment that has big power semiconductors in it, worth hundreds of dollars, each.
Something like:
http://www.irf.com/product-info/datasheets/data/st303c-c.pdf

In that kind of equipment, the fuses are expected to save the semiconductors, and do so, repeatedly, when things malfunction.

If an SCR in a big drive misfires and a fuse doesn't blow and protect the semiconductors, it isn't long before the equipment manufacturer is on the line discussing why the design is so poor, and who is going to pay for the outage. And the person who selected that equipment is explaining why the factory is sitting idle, so long while all those big devices are being unbolted and replaced and re torqued, along with their fuses.

I haven't been in that hot seat, but I have watched others squirm and sweat as they threw the power back on to see if the new set also instantly blew up because they were under the gun and didn't have time to trouble shoot why the first set failed before trying another set.
.

Loading