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Are these fuses past their "best before" date?

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Luk88

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I've managed to "score" some fuses made in 1989 in back then still communist Poland.

They measure exactly the same as new ones I have despite the visible tarnish. Likewise for the holders.

I paid 20% of the usual price. There is no "jest before" date for fuses as far as I can tell. The only difference between these and modern NH00 fuses is the contact electrode. One's made today have a so called "knife" (it really looks like a butter knife scaled 10x bigger). These have this wavy things. I'm planning to watch them on a thermal camera when testing to ensure they dont heat up.

The miliohm meter is there to scale. What do you think? gTF is a fast characteristic. Yes, I'm aware they are for AC not DC and I'm going to use them with ~50V DC. But if they have 100kA short braking capability at 500V AC I'm pretty happy with them for DC. Compress_20240724_163004_4154.jpgCompress_20240724_163004_4405.jpgCompress_20240724_163004_4694.jpgCompress_20240724_163004_4929.jpg
 
It probably works as rated. I don't thing there are too many complaints about Soviet macro electronics.

I did say as rated. It's an AC fuse. DC power is just built different. DC tends to arc much more, so AC fuses with the same rating can have different DC ratings. On the far end of risk, it's possible an AC rated fuse doesn't disconnect far enough to extinguish a DC arc and the power keeps on flowing.
 
I would not be afraid to use them they look to be in excellent shape no signs of exposure to elements that might compromise their integrity most likely contain fine silica should be equivalent to a class T just use 50% voltage rating for DC when not clearly marked to be safe.
 
Citlalatonac said:
It probably works as rated. I don't thing there are too many complaints about Soviet macro electronics.
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SOVIET🫢?

Poland was a part of the communist block at a time, but it never was a part of USSR. Many people would be very upset by being called soviets... The usual meaning being anyone from USSR. The term was widely used within Poland with that specific meaning at the time.

Anyway, I happen to collect old stuff like this, including soviet stuff. The way to tell it apart is by writing and stamps. Essentially if it has latin letters it is almost certainly not soviet. But just having cyrilic letters doesn't prove otherwise as there were countries like Bulgaria that used the alphabet. Highest quality soviets stuff (for military and svientific use usually has a stamp like this). I never saw it on anything manufactured outside USSR.

State_Quality_Mark_Of_The_USSR_(Black).svg.png

Citlalatonac said:
I did say as rated. It's an AC fuse. DC power is just built different. DC tends to arc much more, so AC fuses with the same rating can have different DC ratings. On the far end of risk, it's possible an AC rated fuse doesn't disconnect far enough to extinguish a DC arc and the power keeps on flowing.
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Yes, definitely. Ive been looking for some actual construction details for this class of fuses(ceramic, single piece of wire inside, surrounded by sand or fine crushed glass) between AC/DC, but I found nothing.

I strongly suspect the DC and AC fuses are exactly the same(only talking about t-class, nh00 etc), but derated accordingly.
 
Luk88 said:
SOVIET🫢?

Poland was a part of the communist block at a time, but it never was a part of USSR. Many people would be very upset by being called soviets... The usual meaning being anyone from USSR. The term was widely used within Poland with that specific meaning at the time.

Anyway, I happen to collect old stuff like this, including soviet stuff. The way to tell it apart is by writing and stamps. Essentially if it has latin letters it is almost certainly not soviet. But just having cyrilic letters doesn't prove otherwise as there were countries like Bulgaria that used the alphabet. Highest quality soviets stuff (for military and svientific use usually has a stamp like this). I never saw it on anything manufactured outside USSR.

View attachment 231037


Yes, definitely. Ive been looking for some actual construction details for this class of fuses(ceramic, single piece of wire inside, surrounded by sand or fine crushed glass) between AC/DC, but I found nothing.

I strongly suspect the DC and AC fuses are exactly the same(only talking about t-class, nh00 etc), but derated accordingly.
Click to expand...
Arc extinguishing maybe different when comparing AC to DC I'm not sure

As far as old block items I bought a large consignment of west German drill bits some time in the 90s probably have a few kicking around now damn they were good.
 
ThaiTaffy said:
Arc extinguishing maybe different when comparing AC to DC I'm not sure

As far as old block items I bought a large consignment of west German drill bits some time in the 90s probably have a few kicking around now damn they were good.
Click to expand...
From what I gather the difference in ratings will be lower voltage rating (for example I'd not use these 500V AC fuses with more than 80V DC) and max arc current. I would trust these for up to 25kA short circuit current for example. How did I "guesstimate" these numbers? The same manufacturer has same size fuse for DC rated at exactly that (80V 25kA 400A). That DC fuse costs 6x more and is on permanent backorder. No doubt because of lower sales volume etc. I'd never use an AC breaker in a DC circuit. But for a derated sand filled fuse. I think its is acceptable.

It seems all NH00 fuses are built the same(DC and AC). There is a strip of foil inside with multiple narrow sections. This is all in "sand" (this sand may be silica or other similar materials). From what I read in "Electric Fuses" by Wright this sand eqtinguishes the arc by melting. The heat required to melt it takes away the heat energy from the arc quicker than it is supplied and arc extinguishes. The key factors when designing these fuses are the length of the element, size of the element and amount of sand inside. There are various spring loaded devices that pull the wire/strip away, but from what I read these are not used (except for the indicator) in NH00 fuses.
 
Luk88 said:
From what I gather the difference in ratings will be lower voltage rating (for example I'd not use these 500V AC fuses with more than 80V DC) and max arc current. I would trust these for up to 25kA short circuit current for example. How did I "guesstimate" these numbers? The same manufacturer has same size fuse for DC rated at exactly that (80V 25kA 400A). That DC fuse costs 6x more and is on permanent backorder. No doubt because of lower sales volume etc. I'd never use an AC breaker in a DC circuit. But for a derated sand filled fuse. I think its is acceptable.

It seems all NH00 fuses are built the same(DC and AC). There is a strip of foil inside with multiple narrow sections. This is all in "sand" (this sand may be silica or other similar materials). From what I read in "Electric Fuses" by Wright this sand eqtinguishes the arc by melting. The heat required to melt it takes away the heat energy from the arc quicker than it is supplied and arc extinguishes. The key factors when designing these fuses are the length of the element, size of the element and amount of sand inside. There are various spring loaded devices that pull the wire/strip away, but from what I read these are not used (except for the indicator) in NH00 fuses.
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Makes sense big Clive has some interesting videos on YouTube about testing and teardowns of various fuse taken a look if your interested
 
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