[TX7A]

This may be obvious, but:

If there is a 30amp fuse/breaker on the anode side of a 60 amp-rated diode, and you get an over-load on the cathode side that would normally cause the fuse to blow without a diode installed, will the fuse blow?

and...

If there was a direct short downstream of the diode, would the diode go TU?

Thanks for any clarification.

 

[Sparky]

If the diode and fuse are in series, and the diode is rated for 60 amps and the fuse for 30 amps, the most current the diode will experience is 30 amps because that is the current at which the fuse will blow.

This a little over-simplified, but essentially, to answer your questions: Yes, the fuse should blow, and, No, the diode should not go TU.

 

[Jeff R]

A fast current spike exceeding 60 A might not result in a blown fuse, but it might result in a blown diode. However, most power diodes have significantly higher current ratings for transients - the faster the transient, the higher the current it can withstand.

Power also depends on how well the diode is heat sinked. A diode left hanging in the air will burn up at well under rated current. Any power diode should be thermally bonded to as much heat sinking metal as possible to keep it cool.

 

[TX7A]

Thanks, Paul & Jeff. (I like simple answers. )
Yes, my setup is in series. (working on an e-buss)

Sam

 

[molson309]

What kind of fuse are you using in series with the diode? A slow blow type of fuse might well not blow before the diode does, or - as often happens - the diode fails shorted, THEN the fuse blows, the worst outcome of all!

 

[TX7A]

What kind of fuse are you using in series with the diode? A slow blow type of fuse might well not blow before the diode does, or - as often happens - the diode fails shorted, THEN the fuse blows, the worst outcome of all!

ATO type fuse. I see that fast blow are available, so I'll be sure to use them.