Under the action of a certain high temperature for a long time, the melting point and impedance of the fuse will change, and this change will affect the accuracy of the fuse. This is what we often call fuse aging.

After the fuse is aging, there are certain safety hazards, for example, the normal operation of the circuit will sometimes lead to fuse blowing, easy to disconnect the circuit, resulting in the inability to use electricity normally. If the self-recovery fuse aging, after the circuit failure, the self-recovery of the automatic recovery takes longer time or can not be recovered.

Reasons for fuse aging:

1、the environment temperature is too high

Ordinary fuse holder, the temperature is about equal to 160 ° C (150 ~ 170 ° C) when the tin began to diffuse to the wire; fusible body began to oxidise more violently at a temperature of about 200 ° C (175 ~ 225 ° C). With the oxidation of the fuse from the outside to the inside, many times the diffusion, thermal stress fatigue, etc., the life of the fuse will gradually shorten. Therefore, it is recommended that time-delay fuseholders should not be operated above 150°C for a long period of time, and normal operation fuseholders should not be operated above 175~225°C for a long period of time.

2、 Pulse current

The impact of pulses generates thermal cycling, which results in diffusion, oxidation, and thermal stress of the fuse or accelerates it. Fuseholders also deteriorate as the energy and number of pulses increase. The shock life of a fuse holder depends on the percentage of the 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 shocks.

3、 Contact resistance

The length and cross-sectional area of the pipe clamps, and the connecting wires that the fuse holder is in contact with. The contact resistance between the fuse holder and the pipe clamp is large, which is detrimental to the life of the fuse, and UL standard stipulates that the contact resistance between the fuse and the pipe clamp during the test is less than 3 mΩ. When the contact resistance is large, the pipe clamp does not dissipate heat, but generates heat and transmits it to the fuse.