The service life of a fuse

The design life of a fuse is determined according to the reliability of its materials and the conditions of the environment in which it is used, generally between a few years and a few decades. The design life of a fuse does not represent its actual service life, which is affected by a variety of factors, including the operating environment, load conditions, maintenance, etc.  The use of the environment has an important impact on the life of the fuse. If the fuse is in a harsh environment such as high temperature, humidity and corrosion for a long time, its life will be greatly shortened. When selecting fuses, suitable fuses should be selected according to the requirements of the use environment.

Factors affecting fuse life:

a. Working environment temperature:

High ambient temperature is detrimental to the life of the fuse. Time-delay type (slow-blow type) fuse such as tin ball type, the temperature is about 160 ℃ (150 ~ 170 ℃) when the tin began to diffuse to the wire; fast-blow type fuse fusible body (wire) began to oxidize the temperature of more intense is about 200 ℃ (175 ~ 225 ℃). With the oxidation of the fuse from the outside to the inside, the diffusion of many times, thermal stress fatigue, etc., the life of the fuse will gradually shorten.

Therefore, it is recommended that the time-delay fuse should not work above 150℃ for a long time, and the fast blowing fuse should not work above 175℃ for a long time.

b. Pulse current:

Constant pulse impact will generate thermal cycling, which will result in diffusion, oxidation and thermal stress reduction of the fuse. The fuse will gradually deteriorate with the increase of pulse energy and number of pulses. The anti-impact life of the fuse depends on the percentage of I2t of the pulse to the I2t of the fuse itself; normally, it should be less than 20%, so that the fuse can withstand more than 100,000 times of impact.

c. Others:

For example，clamps in contact with fuses, and the length and cross-sectional area of the connecting wires.The high contact resistance between the fuse and the clamp is detrimental to the life of the fuse. the UL standard states that the contact resistance between the fuse and the clamp during the test is less than 3 mΩ. when the contact resistance is high, instead of dissipating heat, the clamp generates heat and transfers it to the fuse.

Fuse use environment

Fuses should be used in a dry, ventilated environment free of corrosive and erosive gases.

If the fuse is in a harsh environment such as high temperature, humidity and corrosion for a long time, its internal materials are easy to aging, resulting in the shortening of the fuse’s life. When selecting a fuse, the appropriate fuse should be selected according to the requirements of the use environment.

The usage environment also includes the installation location of the fuse and the surrounding electrical equipment. The fuse should be installed in a dry, ventilated location, avoiding too close to other electrical equipment, so as not to affect the heat dissipation and normal operation of the fuse.