PTC resettable Fuses problem

[joseph20480]

Dear community,

 

I'm playing with PTC resettable fuses and i have some trouble.

In effect, i'm not able to retrieve datasheet caracteristics in real life.

 

My PTC reference : Bourns MF-USML/X Series - MF-USML300/6

Vmax : 6v / Ihold :3.0A / Itrip : 6.0A

My test :

My fuses in serial with 1.7r resistor.

Voltage supply 5.1v >>> Current load about 2.7A.

My result

Each time, after 20-30 sec the fuse break. Second thing, if i try to use it again, the sensibility have been change and break after 2-3sec (same load).

 

My question... Where is my error

tell me more is you have an idea.

[HarryA]

 Time plays a big factor with PTCs;

26. Recovery time: The recovery time after PTC thermistor action should not exceed 60S.

see: https://www.ntcsensors.com/Technical_parameters_of_PTC_resettable_fuse/#:~:text=Under limited conditions%2C the highest voltage that the,may be broken down and cannot be recovered.

Also there is an interesting video that discusses PTCs here: https://www.youtube.com/watch?v=eeaqyD3ZYjI

[joseph20480]

Sure... but...

We are agree to say, like me, that my fuse with an Ihold: 3.0A shouln't break at 2.7A ?

I will try to contact Bourns for explication. Understand the phenomena.

 

[HarryA]

Sorry they are beyond me. Why would one use a 3 amp fuse that trips at 6 amps? What does the 15 and 50 amps got to do with it?

How would it allow current that high? Beware there are a lot of fake components out there. I got some ICs via  Amazon.com lately they had the TI symbol on them but also "made in China" on them; never seen TI chips with that on them before.

For other viewers:

[Olivia Duke]

 

 Time plays a big factor with PTCs;

26. Recovery time: The recovery time after PTC thermistor action should not exceed 60S.

see: https://www.ntcsensors.com/Technical_parameters_of_PTC_resettable_fuse/#:~:text=Under limited conditions%2C the highest voltage that the,may be broken down and cannot be recovered.

Also there is an interesting video that discusses PTCs here: https://www.youtube.com/watch?v=eeaqyD3ZYjI/geometry dash

Thank you for sharing!