Thread: Is this a fuse?
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Jeff Liebermann Jeff Liebermann is offline
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Default Is this a fuse?

On Tue, 9 Jul 2019 19:32:42 -0400, Bob Engelhardt
wrote:

It was in a variac, connecting the wiper to its terminal. It had a
connector tab on each end & was inside the sleeve. It's lead colored,
but much stiffer than lead - zinc?. The variac is 20A resistive, 14A
otherwise. It failed with a pop when an end connector came off.

I dunno what else it might be, but it was really inaccessible,
underneath the terminal block - a terrible location for a fuse. And
where would you get a replacement?

https://i.imgur.com/y0RREz0.jpg


I couldn't find anything similar, partly because you didn't supply the
maker and model number of the variac.

The lead colored material is probably zinc steel. Try checking with a
magnet.

Thanks for including a ruler in the photo. However, the photo is too
small and fuzzy to use it to make measurements. My guess(tm) is that
the fuse width is 1/16th inch. Since push on tab connectors were
used, I measured a handy large tab connector at 0.033" thickness.
Therefore, the cross sectional area is:
0.063 * 0.033 = 0.0021 sq-in = 2700 circular-mils
http://www.kylesconverter.com/area/square-inches-to-circular-mils
Looking at a handy wire table:
https://www.engineeringtoolbox.com/awg-wire-gauge-circular-mils-d_819.html
2700 circular-mils is approximately the area of #16 AWG wire. Checking
a fusing current table at:
https://www.powerstream.com/wire-fusing-currents.htm
shows that #16 AWG will fuse at:
Copper 117 Amps
Aluminum 86.7 Amps
Iron 36.0 Amps
Tin 18.8 Amps
My guess(tm) is iron at about 36A.

I doubt that you're going to find a replacement fuse. Find a piece of
similar thickness tin plated steel at the local hobby shop. Something
like this, but either thicker, or use 3 layers:
https://www.acehardware.com/departments/hardware/metal-sheets-and-rods/sheet-metal/5611660
If you can't find any, just take some sheet steel and solder plate it.
For 0.033" 20 or 22 gauge looks about right:
https://www.law.cornell.edu/uscode/text/15/206

Be sure to adjust the numbers for the actual measured dimensions.

Or, you could just replace it with an external 35A cartridge fuse.


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