scr

What does the Ifsm rating of an scr mean?

Reply to
Peter
Loading thread data ...

"Peter"

** I = current, f = forward, s = single, m = maximum.

Generally it refers to the largest, once in a while, *half cycle 50/60 Hz * current pulse allowable.

........ Phil

Reply to
Phil Allison

Thanks So I have a power supply that has a zener diode across the output to trigger an SCR in the event of over voltage....... The power supply's fuse is , say 10 amp. Does the SCR's rating have to be at least 10 amp or will a lower rating one do given that the fuse in the event of a short to ground through the SCR will fail pretty quickly

Peter

Reply to
Peter

"Peter"

** Knew there was a catch to this.

Post the full schematic and all the details an ABSE.

Or else piss off .

....... Phil

Reply to
Phil Allison

Ifsm is defined as "non-repetitive peak forward surge current 8.3ms half-sine-wave"

If you know something about your fuse, you *can* determine whether or not the SCR will clear the fuse without failing, clear the fuse but short-circuit in the process, or just plain old explode.

A fuse is characterised by the amount of energy it takes to melt it; the term used is "I-squared-t" or I^2t. If you have an I^2t figure for your fuse, you can compare it with the SCR's I^2t rating to see which one wins.

If SCR I^2t >> fuse I^2t, the SCR will happily blow the fuse, and keep on ticking. This is what you really want to have happen.

If SCR I^2t

Reply to
Terry Given

^^^^^ or 10ms, but they will tell you in the datasheet.

Reply to
Terry Given

Semiconductors are well known for being great fuse protectors !

So in your sentence above you are speculating a lower rated SCR will not fail (or presumably encounter any harm) whilst the fuse will, by maybe restating the question and critiquing your own logic you may well have answered it.

--
Regards
Mike
 Click to see the full signature
Reply to
Mike

Yeah OK, but what's with the piss off bit? Is there some unwritten rule about posting to this NG that I've missed somewhere?

Reply to
Peter

"Peter"

** Cos YOU are bloody TROLLING !!!!!

...... Phil

Reply to
Phil Allison

How is a request for information trolling? The power supply in question is a Johnson Unit that I've repaired for a friend.

formatting link
The semiconductors only had in house type numbers on them. My p was a genuine question. What seems elementary to you is not to me.

Reply to
Peter

Peter, Is that Phil Allison you are having a discussion with? If so, you are wasting your time trying to reason with him. Just killfile the graceless prick. I did, six months ago and have not missed him. His technical knowledge is quite good but he turns to psychotic abuse for no reason. Or maybe his reason is the gratification of getting a shocked reaction. Whatever. He is a troll and is not worth your trouble.

PH

Reply to
Peter Howard

"Peter Howard"

** Piss off - you know nothing IDIOT.

...... Phil

Reply to
Phil Allison

Reply to
Peter

"Peter"

** Bloody TROLLs like Peter always squeal like stuck pigs when they are OUTED !

....... Phil

Reply to
Phil Allison

Very true, and you have never stopped squealing, have you, troll?

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
 Click to see the full signature
Reply to
Michael A. Terrell

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.