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| fuse for 24vac |
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| djacobow:
I'm designing a project powered by a 24Vac wall-wart. I'd like to add circuit protection. I really like the idea of auto-style blade fuses, like ATO type. They're easy to replace and have the current rating clearly marked for olde eyes. But they are made for 12Vdc, not 24Vac. Now, my impression is that using an AC fuse in a DC application is dangerous, as the fuse might not be able to extinguish an arc. But using a DC fuse in an AC application seems ... OK? But using a 12V fuse in a 24V application is probably not ok, right? My fallback will be regular 250Vac 5x20mm fuses, which I don't like for convenience, but they should be fine operationally. |
| james_s:
It'll be fine. I don't know exactly what the voltage rating of this type of fuses is, but it's very likely higher than 12V. I've seen them used quite a bit in HVAC applications where 24V is the norm. 24V is still low voltage. |
| Gyro:
Your assessment of the difficulty of breaking DC vs AC is correct, for the reason you indicated (arc extinction). I suspect that the main reason for the 12V rating is to prevent people using them in commercial vehicles with 24V DC supply - that would probably cause problems. Given the amount of de-rating needed for an AC fuse on DC, my feeling that using one, particularly a low current one, on 24V AC would be fine. You're well within the SELV limit to, so touchability of the pins wouldn't be an issue. |
| T3sl4co1l:
I would worry more that your wall wart is unable to provide fault current, i.e., it is "impedance protected". But not necessarily well enough by itself to avoid melting or smoking or burning up, for which the fuse would be nice. Tim |
| james_s:
Here, I just looked it up. ATO fuses are rated for 32V. http://www.littelfuse.com/products/fuses/automotive-aftermarket-products/blade-fuses/ato.aspx |
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