Repairing a 100A ceramic fuse

Average: 5 (1 vote)

Huge warning/disclaimer on this one, do not repair a fuse as it may result in property damage, fire, electrocution, injury, death, fatigue, loss of appetite, erectile dysfunction, nightmares, PTSD and/or diarrhea.

Having said that, do not do it unless you find your self in some kind of post apocalyptic scenario where you need to restore power to your oil refinery camp in order to defend your self against raiders.

<--break->This fuse (actually 3 of them) are part of an electric installation powering a three-phase pottery furnace rated at about 60kW. Due to a faulty relay responsible for switching between Y and Δ configuration, two out of three phases where shorted to neutral. These fuses where rated at 100A each so when they blew, well,  let's say there was light.

I started by removing the caps, there is silica and a copper ribbon inside the fuse.

In order to replace the copper ribbon (that's the fusing part of the fuse) i had to calculate the width of the copper ribbon.

Using the following table i calculated the copper width for 99A current by dividing the Area by the copper thickness.

Source: http://www.powerstream.com/wire-fusing-currents.htm

 

AWG Diameter in mm Fusing Current for Copper Wire (Amps) Area in mm²
OOOO 11.684 3196 107.219302577
OOO 10.40384 2685 85.0114082563
OO 9.26592 2257 67.4321448791
0 8.25246 1897 53.4880465606
1 7.34822 1594 42.4086240423
2 6.54304 1339 33.6239732882
3 5.82676 1125 26.6651567947
4 5.18922 945 21.1492050492
5 4.62026 794 16.7657394525
6 4.1148 668 13.2980310814
7 3.66522 562 10.5509114164
8 3.2639 473 8.3668805717
9 2.90576 396 6.6314631936
10 2.58826 333 5.261452847
11 2.30378 280 4.1684240097
12 2.05232 235 3.3081107163
13 1.8288 198 2.6267715716
14 1.62814 166 2.0819647572
15 1.45034 140 1.6520741319
16 1.29032 117 1.3076295889
17 1.15062 99 1.0398093508
18 1.02362 82 0.8229385497
19 0.91186 69.6 0.6530496661
20 0.8128 58.6 0.5188684586
21 0.7239 49.3 0.4115731499
22 0.64516 41.5 0.3269073972
23 0.57404 34.8 0.258805912
24 0.51054 29.2 0.2047148886
25 0.45466 24.5 0.1623541434
26 0.40386 20.5 0.1281007178
27 0.36068 17.3 0.1021724961
28 0.32004 14.5 0.0804448794
29 0.28702 12.3 0.064701478
30 0.254 10.2 0.0506707479
31 0.22606 8.6 0.0401362994
32 0.2032 7.3 0.0324292787
Metric 2.0 0.2 7.1 0.0314159265
33 0.18034 6.1 0.025543124
Metric 1.8 0.18 6.1 0.0254469005
34 0.16002 5.1 0.0201112198
Metric 1.6 0.16002 5.1 0.0201112198
35 0.14224 4.29 0.0158903465
Metric 1.4 0.14 4.19 0.015393804
36 0.127 3.62 0.012667687
Metric 1.25 0.125 3.54 0.0122718463
37 0.1143 3.09 0.0102608265
Metric 1.12 0.112 3 0.0098520346
38 0.1016 2.59 0.0081073197
Metric 1 0.1 2.53 0.0078539816
39 0.0889 2.12 0.0062071666
40 0.07874 1.77 0.0048694589

This chart of Fusing Currents for American Wire Gauge (AWG) wire sizes is data intended for the pleasure of our readers only. Typographical errors, etc. are probable. Please point out errors. The data listed are incomplete and should be used as a guideline only. Please contact manufacturers for the latest data. 

Having calculated the appropriate width i cut a copper ribbon twice that size and reduced it's width at about half length, this way when the fuse blows i can make sure that the copper will fuse at this exact point.

Finally i put the silica back into the ceramic container and replaced the caps.

Did it work? Yes, it handled the current without blowing.

Ok but does it work? Actually yes, since conditions causing short circuit where not resolved, the fuse did blow, so...

 

glqxz9283 sfy39587stf02 mnesdcuix8
sfy39587stf03
sfy39587stf04