Plug Top 13A Fuse

John.G

What is the voltage drop through one of these at say 10A, my basic multimeter, using the 0-200VAC scale, couldn't detect any voltage drop on a extension lead plug top fuse drawing ~ 12A.

Addmagnet

Fuse has a resistance of maybe 0.02 Ohm

V = I x R

V = 12A x 0.02 Ohm

V = 0.24

So, not really surprising your multimeter can't show it.

Deagol

How are you trying to measure voltage drop? Across the plug fuse?? TBH, your question makes no sense.

John.G

Makes sense, so generated fuse heat is 12*12*0.02, 2.88 watts, which presumably will eventually further increase the resistance leading eventully to the fuse "failing".

Lenar3556

https://www.boards.ie/discussion/comment/123968113#Comment_123968113

Volt meter measuring between neutral and the supply side vs the load side of the fuse. Relatively easy to do.

10-10-20

I was surprised to see that plug-top fuses had such a high power dissipation at the rated current.

Now I know.

Deagol

https://www.boards.ie/discussion/comment/123968378#Comment_123968378

I sometimes despair of people being deliberately obtuse on the internet. It makes no sense to measure voltage drop across a load like that to calculate something that could be much easier worked out by simply measuring the resistance of a fuse OR as someone else has done, just google it.

And maybe OP has some reason for asking that completely eludes me, I cannot see why one would care. But I'm open learning something.

OP, any chance you can explain why you're asking this? Just for the sake of my curiousty :)

Lenar3556

https://www.boards.ie/discussion/comment/123970627#Comment_123970627

Who is being deliberately obtuse? You asked how he was attempting to measure voltage drop across a BS1368 fuse and I explained how it would be done.

It could also be established by calculation, if you had all of the data, but that wasn’t the question.

John.G

https://www.boards.ie/discussion/comment/123968471#Comment_123968471

Maybe all EV owners with granny charger cables now know that if the plug top melts or whatever that at least its not caused by the heat from the 13A fuse but only if my readings can be taken as correct which don't bear any realationship to the above.

I measured 10A (DC) through a mini air compressor and my M.meter a fuse volt drop of 0.046VDC on the 0-2V scale and 50 on the 0-200k scale so I assume 0.05VDC drop through the 13A fuse with a 10A load, this equates to a fuse resistance of only, 0.05/10, 0.005 ohms and a heat loss of 0.05*10, 0.5 watts?? seems out by a factor of ~ 10. Google/AI……state that the resistance of a typical BS1362 13A fuse is 4mOhm, what is 4mOhms in OHms??

 

Cerco

https://www.boards.ie/discussion/comment/123972000#Comment_123972000

0.004 Ohms

Bruthal.

https://www.boards.ie/discussion/comment/123970627#Comment_123970627

If you are open to learning, then despairing at someones suggested mothod about how to measure electrical measurements by using real testing, is a bit contradictory. Also, they were not describing how to measure volt drop across a load.

Although i would measure volt drop directly across the fuse itself, rather than N to each side of fuse, for a direct result.

The resistance may change if the fuse warms up under load etc, which will be shown by volt drop when the load is on for a while. If i was, for some reason, trying to find an electrical result such as this, id think actual measuring, more informative than varying google answers.

John.G

Some more earth shaking info.

I had a new B16 MCB lying about and carried out the same test with this 10A DC load, it gave a 0.076V drop, = 0.0076 ohms, 0.76 watts. The MCB also has "MBN 116W" written on it, has this any relationship to short circuit protection or whatever? ( a B20 MCB has "MBN 120W))

Deagol

Standard 13 amp fuse measured as ~0.003Ω.

Cables shorted are 0.083Ω

IMG_2250.jpeg

Hope that helps with your mission OP :D