Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [fuses]

Questions regarding physical fuses. A fuse is a safety device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level. PPTC, PTC, and Polyfuse questions should use the Polyfuse tag. Please keep in mind that repair questions are typically closed if not within the scope of the site and FAQ.

Questions regarding physical fuses. A fuse is a safety device consisting of a strip of wire that melts and breaks an electric circuit if the current exceeds a safe level.

Also known as a fusible link, it is a circuit element that is designed to fail when the fuse rating is met or exceeded. It works on the principal of heating a precisely thinned piece of metal as the current flows through it; too high a current will melt the metal, and the higher the current, the faster the fuse "blows".

Fuses typically are low-resistance until they blow and then they form a "open" (unconnected) circuit. They usually come in two varieties: slow blow and fast blow.

PPTC, PTC, and Polyfuse questions should use the tag.

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Why is the number 63 popular in electronics?

Capacitors have a voltage of 63V (not 60 or 65). Fuses have a value of 63A (not 60 or 65). And there exist more odd values in electronics... Who knows the history of this convention?
Jan van der Zanden
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What causes a fuse to blow, the current or the power?

Fuses and circuit breakers are often specified at a certain current they will 'blow'. Increasing the current will also increase the power. So if a fuse is rated for 12V DC and 20 A, this would be equal to 240 watts. If a different voltage is…
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Slow Blow vs Fast Acting Fuse

Is there any way to tell the difference between a slow blow and a fast acting Fuse? I had one blow in my amp and I know its 125v 5a, but i'm not sure if it is a slow blow or fast acting fuse. Is there any way to discern the difference after one has…
Sean
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Can thin sections of copper traces be used as fuses?

Is it safe to use thin sections of copper traces as one-shot fuses when cost is important, but when it is also vital to protect the rest of the circuitry? Should the solder mask be removed at that location? What about using 0R resistances in small…
Mister Mystère
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Parallel MOSFETs

When I went to school we had some basic circuit design and stuff like that. I learned that this was a bad idea: simulate this circuit – Schematic created using CircuitLab Since the current will almost certainly not flow equally over these three…
BufferOverflow
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What type of glass fuse is this and what does the spring do?

This is a standard sized glass fuse like what cars used before the 80s. I can faintly make out 20A, but I’m not sure what to call it in order to find a replacement. The fuse in the picture has not blown, but it is the only one I have. I don’t…
JPhi1618
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Why did my fuse not blow?

I purchased a few fuses to get familiar with their workings, and I was surprised to see that the 100mA fast-blowing fuses I bought happily conducted up to 215mA (6V power supply, 10\$\Omega\$ resistor), where the filament just started glowing. I…
Duoran
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What not to do with a Multimeter

So I just bought and installed a new fuse for an analog multimeter I scored for free and now it works like a charm. The new fuse is the same rating as the blown one I found inside, which is 0.5A 250V. The meter has a warning symbol consisting of…
Alex W
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Fuses: What are the practical differences between Ceramic and Glass cartridge fuses

What are the practical differences between ceramic and glass tube cartridge fuses? I am trying to find new fuses for a piece of consumer electronics. The original fuses are going out of production. The fuses the original BOM called for are ceramic…
Connor Wolf
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Why are multimeter batteries awkward to replace?

I teach introductory physics labs, and inevitably when we do our labs on introductory circuits or mapping electrostatic potentials, there are one or more multimeters whose batteries die or fuses blow. This is always something of a hassle, since you…
Michael Seifert
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Does it matter if a fuse is connected to the negative or positive terminal of a battery?

I am currently going through the conundrum of where to place a fuse in my DC battery-powered circuit to protect the circuit components and the DC battery. I've been googling for a definitive answer, but I came across diverging opinions... Which one…
DryRun
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How to solder a 70 °C (158 °F) thermal / temperature fuse

For my DMX project (schematics is not important), I soldered this temperature fuse which has just two leads (see picture below). The fuse doesn't work (meaning it does not conduct electricity) ... which of course is logical since my soldering…
Michel Keijzers
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Why did my fuse blow after 3+ years of no problems?

For several years, I've had a solenoid wired to the 24VDC output of a PLC (Rockewell Automation 1769-OB16). To protect the PLC output card, a fast-acting 500mA fuse was installed between the PLC and the solenoid. The fuse has been working without…
CaptJak
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How does a fuse blow at its current rating, regardless of voltage?

I know from reading elsewhere that it's safe to use a fuse with a higher voltage rating when replacing one, so long as the current rating and reaction speed is the same. For example, if a fuse is rated 125V 1A, then a 250V 1A can be used. Let's say…
JYelton
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Why do fuses have a maximum breaking capacity?

Wikipedia told me that breaking capacity is the maximum current that can safely be interrupted by the fuse. I don’t understand why, if a small current can blow the fuse, a bigger current can’t. If the current which is bigger than breaking capacity…
Mei sy
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