Fuse Equations (Preece's Law)
It has been found that the dc fusing current for a straight wire element depends upon it's diameter as given by Preece's Law:
where If is the fusing current in amps, C is Preece's Coefficient for the particular metal in use, and d is the fuse element diameter in inches.
The following table shows Preece's Coefficients for common fuse element materials as well as the diameter of wires of these materials which will be fused by the given current in the table.
|
|
Diameters (Inches) |
|||||
|
Current (A) |
Copper C=10,244 |
Aluminum C=7,585 |
Platinum C=5,172 |
German Silver C=5,230 |
Platinoid C=4,750 |
|
|
1 |
0.0021 |
0.0026 |
0.0033 |
0.0033 |
0.0035 |
|
|
2 |
0.0034 |
0.0041 |
0.0053 |
0.0053 |
0.0056 |
|
|
3 |
0.0044 |
0.0054 |
0.007 |
0.0069 |
0.0074 |
|
|
4 |
0.0053 |
0.0065 |
0.0084 |
0.0084 |
0.0089 |
|
|
5 |
0.0062 |
0.0076 |
0.0098 |
0.0097 |
0.0104 |
|
|
10 |
0.0098 |
0.012 |
0.0155 |
0.0154 |
0.0164 |
|
|
15 |
0.0129 |
0.0158 |
0.0203 |
0.0202 |
0.0215 |
|
|
20 |
0.0156 |
0.0191 |
0.0246 |
0.0245 |
0.0261 |
|
|
25 |
0.0181 |
0.0222 |
0.0286 |
0.0284 |
0.0303 |
|
|
30 |
0.0205 |
0.025 |
0.0323 |
0.032 |
0.0342 |
|
|
35 |
0.0227 |
0.0277 |
0.0358 |
0.0356 |
0.0379 |
|
|
40 |
0.0248 |
0.0303 |
0.0391 |
0.0388 |
0.0414 |
|
|
45 |
0.0268 |
0.0328 |
0.0423 |
0.042 |
0.0448 |
|
|
50 |
0.0288 |
0.0352 |
0.0454 |
0.045 |
0.048 |
|
|
60 |
0.0325 |
0.0397 |
0.0513 |
0.0509 |
0.0542 |
|
|
70 |
0.036 |
0.044 |
0.0568 |
0.0564 |
0.0601 |
|
|
80 |
0.0394 |
0.0481 |
0.0621 |
0.0616 |
0.0657 |
|
|
90 |
0.0426 |
0.052 |
0.0672 |
0.0667 |
0.0711 |
|
|
100 |
0.0457 |
0.0558 |
0.072 |
0.0715 |
0.0762 |
|
|
120 |
0.0516 |
0.063 |
0.0814 |
0.0808 |
0.0861 |
|
|
140 |
0.0572 |
0.0698 |
0.0902 |
0.0895 |
0.0954 |
|
|
160 |
0.0625 |
0.0763 |
0.0986 |
0.0978 |
0.1043 |
|
|
180 |
0.0676 |
0.0826 |
0.1066 |
0.1058 |
0.1128 |
|
|
200 |
0.0725 |
0.0886 |
0.1144 |
0.1135 |
0.121 |
|
|
225 |
0.0784 |
0.0958 |
0.1237 |
0.1228 |
0.1309 |
|
|
250 |
0.0841 |
0.1208 |
0.1327 |
0.1317 |
0.1404 |
|
|
275 |
0.0897 |
0.1095 |
0.1414 |
0.1404 |
0.1497 |
|
|
300 |
0.095 |
0.1161 |
0.1498 |
0.1487 |
0.1586 |
|
|
|
Diameters (Inches) |
||||
|
Current (A) |
Iron C=3,148 |
Tin C=1,642 |
Tin-Lead C=1,318 |
Lead C=1,379 |
|
|
1 |
0.0047 |
0.0072 |
0.0083 |
0.0081 |
|
|
2 |
0.0074 |
0.0113 |
0.0132 |
0.0128 |
|
|
3 |
0.0097 |
0.0149 |
0.0173 |
0.0168 |
|
|
4 |
0.0117 |
0.0181 |
0.021 |
0.0203 |
|
|
5 |
0.0136 |
0.021 |
0.0243 |
0.0236 |
|
|
10 |
0.0216 |
0.0334 |
0.0386 |
0.0375 |
|
|
15 |
0.0283 |
0.0437 |
0.0506 |
0.0491 |
|
|
20 |
0.0343 |
0.0529 |
0.0613 |
0.0595 |
|
|
25 |
0.0398 |
0.0614 |
0.0711 |
0.069 |
|
|
30 |
0.045 |
0.0694 |
0.0803 |
0.0779 |
|
|
35 |
0.0498 |
0.0769 |
0.089 |
0.0864 |
|
|
40 |
0.0545 |
0.084 |
0.0973 |
0.0944 |
|
|
45 |
0.0589 |
0.0909 |
0.1052 |
0.1021 |
|
|
50 |
0.0632 |
0.0975 |
0.1129 |
0.1095 |
|
|
60 |
0.0714 |
0.1101 |
0.1275 |
0.1237 |
|
|
70 |
0.0791 |
0.122 |
0.1413 |
0.1371 |
|
|
80 |
0.0864 |
0.1334 |
0.1544 |
0.1499 |
|
|
90 |
0.0935 |
0.1443 |
0.1671 |
0.1621 |
|
|
100 |
0.1003 |
0.1548 |
0.1792 |
0.1739 |
|
|
120 |
0.1133 |
0.1748 |
0.2024 |
0.1964 |
|
|
140 |
0.1255 |
0.1937 |
0.2243 |
0.2176 |
|
|
160 |
0.1372 |
0.2118 |
0.2452 |
0.2379 |
|
|
180 |
0.1484 |
0.2291 |
0.2652 |
0.2573 |
|
|
200 |
0.1592 |
0.2457 |
0.2845 |
0.276 |
|
|
225 |
0.1722 |
0.2658 |
0.3077 |
0.2986 |
|
|
250 |
0.1848 |
0.2851 |
0.3301 |
0.3203 |
|
|
275 |
0.1969 |
0.3038 |
0.3518 |
0.3417 |
|
|
300 |
0.2086 |
0.322 |
0.3728 |
0.3617 |
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