Fuse testing

[Bitsyncmaster]

That fuse that I tested and failed was marked BUSS ATO. Don't know what the BUSS part number is.

I wonder if the "LITTLE FUSE" manufacture does the same thing.

[Bitsyncmaster]

I found a 20 amp brand name LITTLEFUSE in my spare fuse bag. Has some numbers marked on the fuse 257 and 0591M so have to reserch those numbers. But what you see is the the element in this fuse is a heavy bar shaped in a "mound" and the BUSSMAN fuse the element is shaped in a "Z".

The LITTLEFUSE popped without glowing and without melting any of the plastic casing. So guess which fuses I'm going to make sure my car has?

Edit.
Looks like my DMCH fuse block came with LITTLEFUSES. I just need to but some non standard amp ratings I now use and did not come in the kit.

[Ron]

Great stuff!!!

[Bitsyncmaster]

The LITTLEFUSE #257 went obsolete a few years back and is replaced by the #287 types.

So the part number for the 20 amp is:
0287020PXCN

Price from Mouser is $0.232 each when you buy 10

Just for "grins" I ran another test on another BUSS 20 amp fuse and got the same red glow and melting plastic after 7 min at 24 amps.

[Bitsyncmaster]

Here is the best price I've found on the internet. If your buying a lot of fuses (replacing them every year) you get them for 7.8 cents each.

http://www.waytekwire.com/products/1...ATO---ATC-Fuse

[novadmc]

I found a 20 amp brand name LITTLEFUSE in my spare fuse bag. Has some numbers marked on the fuse 257 and 0591M so have to reserch those numbers. But what you see is the the element in this fuse is a heavy bar shaped in a "mound" and the BUSSMAN fuse the element is shaped in a "Z".

The LITTLEFUSE popped without glowing and without melting any of the plastic casing. So guess which fuses I'm going to make sure my car has?

Edit.
Looks like my DMCH fuse block came with LITTLEFUSES. I just need to but some non standard amp ratings I now use and did not come in the kit.

for what it's worth, the 30A fuse in #14 on my car was a LITTLEFUSE (as were most of the ones i recently replaced. All replaced with Bussman ATC fuses) and it was showing signs of melting/bubbling yet hadn't popped. that said, apart from the very noticeable oxidation on the them, i have no knowledge of the age of the the replaced fuses.

[novadmc]

for what it's worth, the 30A fuse in #14 on my car was a LITTLEFUSE (as were most of the ones i recently replaced. All replaced with Bussman ATC fuses) and it was showing signs of melting/bubbling yet hadn't popped. that said, apart from the very noticeable oxidation on the them, i have no knowledge of the age of the the replaced fuses.

i meant fuse #11. god im tired tonight.

[Bitsyncmaster]

The fuse is a resistor that produces heat. When that heat reaches the melting point of the metal element in the fuse than it should open the circuit. Lower amp rated fuses have more resistance to produce the heat required to melt the element with less current. It’s just a smaller cross sectional area of the element.

So a fuse running near it rated current will be running the hottest temps. So if your #11 fuse is melting I would check the current in that circuit and decide if the fuse should be increased in it’s rating to run cooler. That is assuming your fuse connections are clean and tight. Elvis did a study of that #11 fuse melting about 8 years ago and decided it should be increased from a 20 amp to a 25 or 30 amp. The Europe owners had to install higher power high beam lights which pushed the current to high in the 20 amp fuse.

Just ran a voltage drop test over a 20 amp LITTLEFUSE. The voltage was measured at the base of the fuse after running at each current for 2 min.

10 amps. 0.0373 volts = 0.373 watts of heat
15 amps. 0.0625 volts = 0.9375 watts of heat
20 amps. 0.0990 volts = 1.980 watts of heat

Same test with a 20 BUSS.

10 amps. 0.0419 volts = 0.410 watts of heat
15 amps. 0.0689 volts = 1.0335 watts of heat
20 amps. 0.1127 volts = 2.254 watts of heat

[Bitsyncmaster]

You would think I'm testing the fan circuits for a manned space craft mission.

I made up a short circuit connector to plug into the two pin fan connector near the fans up front. I attached my clamp on current meter onto that short circuit jumper and fed the current meter output into my oscilloscope.

I install the following fuses into my fan fail unit, started the engine and switched on the AC. Note these are LITTLEFUSE fuses but the BUSS brand looks like they have the same type of protection element so BUSS brands may also be good for the ATM type fuses.

1o amp fuse, 55 amps peak current held for 12 ms.
15 amp fuse, 55 amps peak current held for 32 ms.
20 amp fuse, 55 amps peak current held for 41 ms.

I did this testing to decide if I can make an electronic fuse that works that fast or faster. Also wanted to test if the fuses work fast enough to protect the current sensors in my fan fail unit which they did.

[Bitsyncmaster]

Well I made a mistake when I said the currents peaked at 55 amps. It's really 110 amps which explains why the fuses popped so quickly. My clamp meter puts out 0 to 2 volts which relates to the selected scale of 20 amp or 200 amp ranges. Doing the modification on the scale on my scope I made the mistake.

Anyway, I wanted to test it with a 30 amp fuse.

30 amp, peak current of 110 amps, popped the fuse after 124 ms. And my current sensor in the fan fail is still working fine. It's rated for 20 amps continuous and one 100 ms transit at 100 amps.