EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: calzap on February 26, 2024, 07:08:36 pm
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After watching a couple of videos on poor performance of no-name auto fuses, I decided to go through my collection to see if I had any of these rascals, and yes, I did. Main group was a collection of 2-blade mini fuses bought on Amazon or eBay. Fortunately, I have a HP 6023A power supply which provides CC operation up to 30 A. I would warm-up a fuse at ½ rated amps for a couple of minutes then over about 30 sec, increase to 1.5x rating. It was acceptable if the fuse blew either before reaching 1.5x rating or 30 sec after. If it didn’t blow within 60 sec after starting to increase amps, I kept increasing at 2-5 minute intervals until it blew.
Results on the collection of no-name mini fuses was sobering. The 5-amp fuse took 14 A to blow. The 10-amp and higher never blew even at the max setting of the PSU, which was 31.6 A! The whole collection was tossed.
I had few fuses, full-size, two-blade or two-slot, that were no-name and 25 A and up that couldn’t be tested on the HP PSU. Wasn’t worth the effort and cost to use one of my high amperage 12 V supplies and high-power resistors to test them. So, they were tossed. Also had a few low-amperage no-name 2-blade mini or full-size fuses that weren’t part of a collection, and they all tested OK.
Nearly all the name-brand fuses were Bussmann and Littelfuse, and did not feel the need to test them. Have a collection of full-size 2-blade Neiko fuses which have no logo on the fuses themselves. To my surprise, they passed the test. However, I will only buy fuses in the future that have a trusted logo on the fuses themselves. Logos on fuses for Bussman and Littelfuse are BUSS and LF.
But there were a few fuses, not part of a collection, that had a logo of an uppercase G within a circle that tested OK. The pic below is a representation of the logo. Anyone know what brand these might be?
Mike
[attachimg=1]
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Hi Mike, what standard are you using for your identified compliance levels of current and time? Eg. SAE J2077 or ISO 8820-3 ?
Why didn't you test some fuses that you knew were specified to be compliant, as a form of verification of your test technique?
Ciao, Tim
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Not sure if you’re joking about following SAE or ISO standard tests. It was just a crude go/no-go test, and hardly a lab QC exercise. Basically, I looked at the time versus amperage curves published by Littelfuse as well as what folks have done in youtube videos. Somewhat embarrassingly, I did test a few Littelfuse fuses before I looked closely with a magnifying glass and saw the small LF logo. Had to go trashcan diving because some had been tossed. Also checked that the V and A displays of the HP PSU agreed with a Klein multimeter (up to 10 A … the limit of the Klein).
A few years ago, I learned not to test continuity of fuses rated 100 mA or less with continuity function of a multimeter. :-[
Mike
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I wonder if my collection of 20x5mm glass fuses fare any better. Todo.
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Curves are just average. Did you check a Littlefuse data sheet to identify the limits they have to comply with? Most limits are very wide, so it may be that your fuses operated within limits, even though each fuse operation appeared to be unacceptable to you.
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Yeah, I did look at tolerance specs. And they did play at least a subconscious role in the go/no-go criteria that were used. However, tolerance specs aren’t needed to decide that 5 A fuses that never blow at 12 A and 10 A fuses that never blow at 30 A are tossers. In the end, it was only the collection of no-brand mini fuses that did not test similarly to name-brand fuses.
It’s a little scary to think about the no-brand small cylindrical fuses I have, many salvaged from equipment. Someday, I’ll test them. Most of the cylindrical fuses I use in test and other equipment are good name brands.
Mike
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Fuse manufacturer ratings can certainly be quite varied. A Bussman ATC datasheet indicates up to 4 minutes at 135% rated, whereas a USA Optifuse APR datasheet indicates up to 30 minutes, for auto blade fuses. Certainly at 2x or 3x rated the blow time should be down in the low seconds range.
One concern for diy is that few people retain the original manufacturer details with the actual fuses purchased, and typically put all sorts in a generic bucket for eg. 2A. There is certainly a significant difference in specs for 5x20mm etc UL (USA based) fuses compared to IEC (europe and a lot of other countries) fuses, and imho they definitely should be kept separated.