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Discussion Starter #1
Are the fuses in say a newer car or truck considered the slow-blow type or quick-blow? I'm talking about the different colored plastic fuses.
I would think they're more of a quick\fast-blow type fuse.
If one of them is rated at 30A, at what current would it blow and how quickly?
 

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They are all quick these days. Slow ones had a heatsink material wrapped around the element to make it melt slower (a second or two). A circuit breaker would be a good modern alternative.
 

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Discussion Starter #3
That's what I figured Jim. I know what a slow-blow looks like but have never seen one in an automotive setting. I figure an automotive fuse will blow right at or close to the rated current stamped on them.
The reason I'm asking is because I'm going to test some 30A fuses and see how much they can take. I expect them to POP right away but without doing some surfing and looking for more info, I wondered if anyone knew a little more about how they respond to over-current.
And no, I'm not putting some massive power drawing system in a car or anything.
;)
 

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In comparing the ATO's to the older AGC's, ATO's will melt at a slower rate than AGC's, but not much slower.

Take video of both and watch frame-by-frame and time it. Let us know of your science project.
 

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In comparing the ATO's to the older AGC's, ATO's will melt at a slower rate than AGC's, but not much slower.

Take video of both and watch frame-by-frame and time it. Let us know of your science project.
That sounds like fun! We're not very busy at work at the moment. Maybe I can blow a few fuses and record them with our high-speed digital cameras. I could also put timing on them to see exactly when they blow.
 

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Test them like the Government ;)
'Take fuse up to 25% over it's rated value - if it 'blows' mark it as "Good" and proceed to next fuse' :D
 

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Discussion Starter #7
Actually John, you're not far off what the actual specs are.

A 30A fuse for your car is rated at 32volts. They are also considered 'fast-blow'. Now, they're not going to pop at 30 amps. They can hold 30 amps for 100 hours at ambient temperatures. :)
Then all kinds of factors come into play before they'll open up.

I pumped one up to 35 amps yesterday and it just sat there. That was at well over 20 volts. I didn't shock it at 35 amps, but ramped it up slowly until I got there. That way I could see when it started to deform or break. I set the o-scope to trigger and hold the timing of when the voltage started to drop off and then die so I could see how long it took to open. But it didn't pop and I went on to other things for a while.
I'll be coming back to this soon enough though.
;)
 

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The fuse kits you can buy from harbor freight are supposed to have problems with their rating...

Dale

Yeah, the Chinese don't know much about amp ratings l:)

Oh, and their 20ton press a friend has only put @14tons pressure on a calibrated load cell - none of us were surprized though ;)
 

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..set the o-scope to trigger and hold the timing of when the voltage started to drop off and then die so I could see how long it took to open...
You're a nerd Joe :D ...not that there's anything wrong with that. That's exactly how you know for sure. We need a new forum to hold these types of mythbuster product tests.
 

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Are you using a storage scope to hold the display?
Using a regular triggered scope, display will last until the end of the trace and disappear.
 
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