How To Select Fuse

The fuse can be selected according to the following process:

A. Determine the safety mark: according to the market requirements of the product to be sold, select the safety certification mark and safety standard of the fuse (UL standard or IEC Standard Fuse)

B. Determine the overall size: select the overall size of the fuse according to the installation space, the determined safety certification mark and safety standards

C. Determine the model: select the model of fuse according to the current characteristics of the protected circuit. For example, if the current characteristics of the protected circuit are constant current, select the fast fusing type

D. Determine the rated voltage: determine the rated voltage of the fuse according to the input voltage and use requirements of the protected circuit, such as 350V; However, considering the cost factor, it is not necessary to select too high rated voltage

E. Determine the minimum rated current: preliminarily determine the rated current of the fuse according to the stable working current of the protected circuit and the similar use loss coefficient. For example, the steady-state working current of the protected circuit is 1a, select UL standard time-delay fuse, and the working ambient temperature is about 25 · C, then the minimum rated current of the fuse is 1A * 1.25 = 1.25A

F. Determine the minimum it of the fuse tube, and determine the IT of the fuse according to the surge it of the protected circuit. For example, the surge it of the protected circuit is 1 (as). In order to protect the fuse tube from more than 100000 shocks, the IT of the fuse should be greater than: 1 ÷ 0.2 = 5 (as)

G. Determine the rated current of fuse: according to the minimum rated current and minimum it value, check the corresponding model and specification in the product catalog, and take the primary rated current specification that is greater than the minimum rated current value and its IT value is also greater than the minimum it value as the rated current of the selected fuse. For example, according to the above minimum values, (1) for example, the it with rated current of 2.5A is 4.3as, the it with rated current of 3a is 5.4as, Then 3a is the rated current of the selected fuse; (2) If the IT of the rated current 2a is 5.3as, then 2.5A is the rated current of the selected fuse

Start - Safety Certification - rated voltage - structural size - breaking capacity - preliminarily selected model - selected rated current - specific model and specification - Test - end

test

The selected samples must be tested in the actual protected circuit to verify the selected fuse. This verification shall include tests under normal and fault conditions to ensure that the selected fuse plays a protective role in the protected circuit.