Will fuse blow....with repetitive overcurrent pulses?

[eem2am]

Hi

We are using the 500mA fuse of this series (Littelfuse 452 series)

FUSE DATASHEET:
**broken link removed**

The current flowing in this fuse will be as follows

CURRENT WAVEFORM:
https://i55.tinypic.com/2ed9hf8.jpg

its peak is 1.2A
its ON for 6.2us, then OFF for 31us...repetitively

The current average value is 204mA.
The current RMS value is 494mA.


This current waveform will flow continuously,
-will the fuse blow?
-or will we encounter occasional nuisance tripping?

the datasheet explains what would happen for single overcurrent events....but not for repetitive overcurrent pulse streams.

 

[IanP]

Fuses act on rms current over certain period of time, so I think in this case 500mA-rated fuse working @ 495mA-rms current may, or may not blow, that will vary from fuse to fuse as the current is just to close to the fuse’s rating ..
You’d better select a fuse that is rated one size up, that is 630mA, and this one should work fine ..

IanP
:wink:

 

[pauloynski]

For a 100% ampere rating the datasheet guarantees a minimum opening time of 4 hours only. And as IanP has pointed out, the nominal melting is defined by I2t (A2sec), so, it the RMS current that counts. So, it is better going for a higher rated fuse.

 

[dick_freebird]

Yes, electromigration will happen. Current and temperature
accelerated. Your manufacturer ought to have reliability
data of this sort available, though you might have to dig
or ask nicely.