Three Standards for the Definition of "Good" Chip Fuses.fast acting vs fast blow fuse

　　The first function of a patch fuse is protection, which means that when protection is needed, the patch fuse should play a role. This is also the first consideration when choosing a patch fuse. In general, the rated current of a fuse must be greater than the normal working current of the circuit and have a certain overload capacity. However, if the margin is too large, it will reduce or weaken its protective function. When a patch fuse should be activated, it should not act, causing damage to the protected components or even more serious dangerous consequences. The main reference tool for designers when selecting patch fuses is the "time current characteristic curve" in the product specifications provided by the fuse manufacturer.

　　Choosing the appropriate type of SMD fuse with appropriate fusing characteristics and the appropriate rated current specification can meet the protection function of the fuse.

　　The second function of SMD fuses is their load-bearing function, which is commonly referred to as their pulse resistance. This is an important parameter that we must also consider when selecting SMD fuses. During the use of fuses, there is a greater chance of normal current fluctuations or instantaneous pulses than fault overcurrent. Therefore, in a sense, this consideration is particularly important and practical for the use of fuses. As long as the melting heat energy value I2t of a fuse is greater than the energy of the circuit pulse, the fuse can withstand it. The "time melting heat energy curve" is a tool provided to designers to evaluate the pulse resistance when selecting a fuse (which can also be in the form of a current melting heat energy curve). Furthermore, even if the fuse does not blow during pulse impact, it will be damaged to some extent. In other words, at this time, the I2t of the fuse will decrease, That is, the ability to withstand pulses has decreased, so when selecting a fuse, it is also necessary to consider this attenuation factor. Usually, a simple calculation requires a margin of 3-5 times to ensure that the fuse has sufficient pulse resistance. There is a contradiction between the pulse resistance of a fuse and its protective performance. We must find a reasonable balance between these two aspects and find the best combination point. To meet the load-bearing function (pulse resistance) of the fuse, it is necessary to choose a fuse variety and specification with appropriate melting heat value and amplify it with sufficient and reasonable safety margin.

　　The third function of patch fuses is safety. A high-quality and reliable fuse should ensure safety before, during, and after its operation, that is, safely conducting and safely fusing. The main technical indicator that can ensure the requirement of a fuse is its breaking capacity. Breaking capacity refers to the maximum current that a SMD fuse can safely cut off a circuit, usually referring to short-circuit current. The SMD fuse must be able to break the circuit absolutely safely when encountering short-circuit current, that is, without any unsafe factors during the breaking process, such as continuous arcing, multiple conduction, breakage, splashing, combustion, and even explosion. The breaking capacity of each fuse must be greater than or equal to the maximum short-circuit current of the protected circuit. The rated voltage of a fuse determines its withstand voltage and is another indicator of its safety performance. It can only be used in circuits with a working voltage less than or equal to the rated voltage of the fuse.

Read recommendations:

motor thermostat overheat

51x80 European body breaker

70H

vizio tv fuse location.How to choose a fuse for safety?

automotive blade fuse dimensions.How to choose a suitable fuse?