Mains Breaker Instead of Fuse?

[defaced]

Is there any liability associated with replacing the mains fuse with a slow breaker? Here's the one I'm looking at: W28-XQ1A-5

[Enzo]

They are used as mains breakers in many things. They are rated to 250VAC.

[Robert M. Martinelli]

The only issue I can think about is the time they need to trip, if you're willing to replace a slo-blo fuse I think they're OK, but they cannot be as fast as a fast blow fuse.

Cheers

Bob

[Steve Conner]

Depends what you mean by "liability". If you mean legal liability for a product you're going to sell commercially, well, we don't even go there.

If you just meant "is there anything wrong with doing it" then I guess there isn't. Breakers tend to be for large high-powered apparatus where you expect them to be popping now and again, and it would be a hassle to replace a fuse.

For instance, I have a 1000 watt switching power supply with a pop-out breaker on the front panel. The line current draw of a SMPS actually increases as the line voltage sags, and I think if the line sags below 100V while the output is fully loaded, the breaker is supposed to pop before the guts overheat and blow out. No breaker or fuse can protect semiconductors against serious short-circuts and the like, but it has electronic current limiting for that.

[tedmich]

here's someone's Ph.D. talk on the issue:
http://www.ieee.li/pdf/viewgraphs/ov...protectors.pdf

little "thermal" circuit breakers are temp sensitive, slow and inaccurate.

true magnetic are the bomb, but big and $$$
http://media.digikey.com/pdf/Data%20...PDFs/808-H.pdf

this one is $30 at Digikey

[defaced]

Thanks for the feedback. I'm glad to see there wasn't a fundamental error in my thinking. This won't be for a product, I'll leave that to the people who know what they're doing. BTW, that presentation is very interesting. I've always been curious about the ins and outs of fuses and breakers.

Mainly, I'm just lazy/forgetful and don't won't to forget about fuses if I'm out and be SOL, or have a trouble shooting session where I eat through 10 fuses. By that point in time I could have just bought the breaker and saved some cash. At the same time, I don't want to replace a PT either or have a breaker that doesn't reset because it's junk.

So since these are slower, I'm only using this for the mains fuse which should be a slow-blo any way. Also, this will be for a toroidal power transformer, which if I remember right has a high in rush current, so the breaker being slower than a fuse might help me. We'll see. For a couple of bucks, the breaker is at least worth checking out so I'll buy one and run it through the ringer.

So... if anyone has any tests or knows of any standards to evaluate breakers and fuses, let me know and I'll see what I can do. I've got access to an endless library at work, so I can at least try to get standards.

[Grun]

Traynor used breakers instead of fuses. I was shunt biasing my YGL3 and the probe slipped, the breaker saved me $0.50 in fuses and $2.00 in gas lol.