So what is an APR fuse?

[micky]

Douglas · May 17, 2018 says: According to Littlefuse, the inventor of the ATO fuse, the idea that ATO means OPEN and ATC means CLOSED is a myth. When Littlefuse applied for patent rights for the fuse name, they could not patent AUTO, which they wanted to do since the fuse is intended for vehicle use. So they patented the name ATO for Auto.

Littlefuse's competitors obviously could not use the ATO name, so they came up with ATC. Whether the myth of ATO=open and ATC=closed came from those competitors is not clear. However, you will find that ATO is still a trademark for Littlefuse, and ATC uses can be found with both closed and open bottoms - which pretty much debunks the myth.

So what is an APR fuse?

but it doesn't say! Not even it its glossary or selection guide.

It seems to have something to do with how fast the fuse blows, but the first link describes the whole category as Fast Acting/Blade Mounting.

I think the graph is bragging that they do blow quickly, not saying that they are in any way slo-blo.

Or maybe they are saying they blow within a range of time, but then how is that different from ATC or ATO?

[gfretwell]

ATC and ATO are just made by different manufacturers but follow the same standards.

Fuses are generally designated by a 3 character type. This is just the tip of the iceberg but it will get you started. There are dozens more types of fuses in just about any amperage you want.

[micky]

Yes, ATO was trademarked by Littelfuse, although now Littelfuse might be moving to ATOF (tin plated) and ATO Ag (silver plated).

WADR, I was already started. I asked what an APR fuse was.

Alas, that page just lists APR fuses along with ATO and ATC, and doesn't say a word about what makes APR different from others.

"Regular (APR / ATC / ATO / ATS)"

[gfretwell]

Since your Google seems to be broken, let me help APR is a generic replacement for ATO / ATC fuses (trade names registered to Littelfuse / Bussmann respectively).

They all meet the same standard, just different manufacturers.

[Ralph Mowery]

I do have to disagree with you on that. The ATC and ATO are two different ways of making the blade type car fuses. The ATC is a closed fuse element so that water can not get in and cause corosion. The ATO has an opening where the fuse element is and water can get in.

There is an APR fuse that is suppose to be a replacement for both of the above.

I have not verified it, but I am thinking the is for the blade type fuses and they are only rated for 32 volts. I may be off on the voltage, but it is more than 24 and less than 50 volts DC.

[Clare Snyder]

NOT true. It is branding only. Littlefuse vs Bussman ATO was available for registering - Auto was not - so Littlefuse registered ATO as it's "auto" fuse. When Cooper Industries Bussman division got into the market they used ATC for AT style COOPER.

32 volts for 24 volt vehicular electical systems Also APS, APM, APR and APX Automotive Protection Small, Automotive Protection Mini, Automotive Protection Regular and Automotive Protection Xtra for small, mini, regular and Maxi.

There is also the theory (unproven to this point) that the AP stands for Anderson Products - another large Automotive fuse and device supplier (now Impulse Electronics) - manufacturer of, among other things, the PowerPole quick disconnect power connector that has established several "standards" in the low voltage DC sphere.

[Ralph Mowery]

It seems to be acombination of both. One is branding as a trademark by companies, and there is a difference in the way they are made. One completely closed in plastic and one with the element exposed to air. Maybe a paten problem, I don't know.

[Ralph Mowery]

The ATO was origionall used because the AT(some other letter I forgot but think it was an A) was already a trademark so the O was used and thought to be a subsitute for auto or automobile.It seemed to have later been called closed.