Ampere-second characteristics of the fuse

What does the ampere-second characteristic of the fuse mean? Here is a brief explanation.

 The action of the fuse is realized by the fusing of the melt. When the current is large, the time required for the fusing of the melt is shorter. When the current is small, the time required for the fuse to fuse is longer, and it will not even fuse. Therefore, for the melt, its operating current and operating time characteristics, that is, the ampere-second characteristics of the fuse, are inverse time characteristics. Each melt has a minimum melting current. Corresponding to different temperatures, the minimum melting current is also different. Although this current is affected by the external environment, it can be ignored in practical applications. Generally, the ratio of the minimum melting current of the melt to the rated current of the melt is defined as the minimum melting coefficient. The melting coefficient of commonly used melts is greater than 1.25, which means that the melt with a rated current of 10A will not fuse when the current is below 12.5A. The relationship between fusing current and fusing time, for example:

Fuse current 1.25~1.3IN 1.6IN 2IN 25IN 3IN 4IN

Fusing time ∞ 1h 40s 8s 4.5s 2.5s

It can be seen from this that the fuse can only play a role of short-circuit protection, not an overload protection. If it is really necessary to use it in overload protection, the rated current used must be reduced. For example, 8A melt is used in a 10A circuit for short-circuit protection and overload protection.