What factors affect the life of the fuse?

Factors affecting the life of the fuse: a. Working environment temperature: Too high ambient temperature will damage the life of the fuse. Time-delay type (slow-blow type) fuse such as tin ball type, when the temperature is about 160℃ (150~170℃), tin starts to diffuse into the wire; the fusible body (metal wire) of fast-blow type fuse begins to oxidize more severely The temperature is approximately equal to 200°C (175~225°C). With the oxidation of the fuse from the outside to the inside, multiple diffusion, thermal stress fatigue, etc., the life of the fuse will gradually shorten. Therefore, it is recommended that the time-delay fuse fuse should not work above 150℃ for a long time, and the fast-blow fuse should not work above 175~225℃ for a long time. b. Pulse current: The continuous pulse impact will produce thermal cycles, which will cause the diffusion, oxidation, and thermal stress of the fuse to occur or even accelerate. The fuse will gradually age as the pulse energy and frequency increase. The impact life of the fuse depends on the percentage of the pulsed I2t to the I2t of the fuse itself; usually, it should be less than 20%, so that the fuse can withstand more than 100,000 impacts. c. Others: Such as the pipe clamp in contact with the fuse, and the length and cross-sectional area of the connecting wire. The contact resistance between the fuse and the tube clamp is large, which is detrimental to the life. According to the UL standard, the contact resistance between the fuse and the tube clamp is less than 3mΩ during the test. When the contact resistance is large, the pipe clamp does not dissipate heat but generates heat and transmits it to the fuse. 2. The influence on the use after the fuse is aging: After the fuse is aging, there will be no danger of the current that should be cut off and the fuse will not blow. After the fuse is aging, it is equivalent to a decrease in the rated value (current) instead of an increase, so there will be no safety problems in the circuit, but the circuit will be cut off under a small overload current or pulse. 3. Test and evaluation of fuse life: "Endurance test method" is stipulated in the IEC standard, but there is no similar stipulation in the UL standard.

The endurance test in the IEC standard is the life test. The method is to use a DC power supply test at normal temperature:

1. Measure the voltage drop under the rated current until the temperature is stable;

2. 1.2 times the rated current for 1h, cut off the current for 15min. Cycle 100 times;

3. Power on 1.5In 1h to measure the voltage drop;

4. Measure the voltage drop in the same way as in 1. Requirements: The voltage drop before and after the test should not exceed 10%, and the mark is still clear and discernible, and there is no deterioration in the solder joints of the end caps.