PTC Resettable fuses?

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UnlikeKurt
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PTC Resettable fuses?

Post by UnlikeKurt » Mon Sep 24, 2012 1:43 pm

Hello all.

I am wondering abit about PTC resettable fuses. I understand their function (thyristors) after some reading. but i'm not sure how i would go about select one to replace a glass fuse.
For instance, where i currently use a 1.5A fast blow in an amplifier, would i be able to replace it with one of these devices? There seem to be a lot more specifications involved than simply 1.5 fb.

thanks!

Nate Dort
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Post by Nate Dort » Mon Sep 24, 2012 2:41 pm

Curious as to why you would want to replace a glass fuse with a PTC in the first place? Hard to access? Are you having to replace it all the time? There are much better solutions for both of those.

Speaking with a few years of experience designing 12VDC power systems filled with PTC fuses, they usually don't blow fast enough to adequately replace a glass fuse.

Example: A 1.5A PTC (TE Conn. LVR075S) with a voltage rating of 125VAC takes up to 18 seconds to blow with 3.5A running through it. Might be substantially longer at 1.5A. I'm not comfortable with my amp smoldering away for 30 seconds until the PTC trips.

Check out the third page of the datasheet for the LVR075S here. None of them have a max break time less than 10 seconds. That's way too slow to replace a fast-blo glass fuse.

UnlikeKurt
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Post by UnlikeKurt » Sun Oct 07, 2012 8:31 am

Thanks for the response nate!
It seemed like a cheaper alternative to glass fuses but after reading your post and the data sheets it doesn't seem like something you'd want to have in an amplifier. a blown fuse is a warning call.

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