What are the operating characteristics of fuses used in motor circuits?

Update:11 May 2020
Summary:

  The action of the liming motor circuit using a f […]

 

The action of the liming motor circuit using a fuse is realized by the fuse of the melt. When the current is large, the time required for the fuse of the melt is shorter. When the current is small, it takes a long time to melt the melt, and it will not even melt. 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. It is generally defined that the ratio of the minimum melt current of the melt to the rated current of the melt is the minimum melting coefficient. The melt coefficient of the commonly used melt is greater than 1.25, which means that the melt with a rated current of 10A will not melt when the current is below 12.5A.

It can be seen from the above situation that the fuse can only play the role of short-circuit protection, not overload protection. If it is really necessary to use it in overload protection, the rated current must be reduced. For example, 8A melt is used in 10A circuit, which is used for short circuit protection and overload protection, but the overload protection characteristics at this time are not ideal.

 

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