Eight Major Considerations for Fuse Selection

Eight Major Considerations for Fuse Selection

1. Determine the size and shape of the fuse according to the circuit space: SMD, miniature, ultra-small, ceramic, glass tube, etc.

2. Determine the required safety certification: C-UL, VDE, SEMKO, PSE, CCC, KC, BSI, etc.

3. Rated voltage:

When the fuse is working normally in the line, its power consumption is very small, so its voltage drop is also very small, but when the line fails and the fuse is blown, the two ends of the fuse will bear the rated voltage of the line. Greater than or equal to the rated voltage of the line is one of the factors in choosing a fuse link.

4. Rated current:

The rated current of the fuse-link is the current that the fuse-link can work normally under laboratory conditions. Because the North American (UL, CSA) standard and the European (IEC) standard have different views on the fuse-link design, when selecting the current value of the fuse-link To follow the formula:

North American standard fuse link:

Fuse current value ≥ normal working current of the line / 0.85

IEC standard fuse link:

Fuse current value ≥ normal working current of the line

5. Breaking capacity:

The fuse will melt and disconnect when the fault current passes through, cut off the fault current and then flow, but if the fault current is far greater than the voltage and current that the fuse can withstand, the fuse itself will explode and endanger the surrounding environment or components. The maximum fault current that the fuse itself can withstand under the rated voltage is called the breaking capacity of the fuse. The fuse link manufacturer will indicate the maximum fault current that the fuse link can withstand. When selecting the fuse link, the user should estimate the maximum fault current value that may occur in the line. The fault current must be less than the breaking capacity of the fuse link

6. Attenuation rate of ambient temperature:

When the fuse is used in an environment of 25±5℃, the rated current of the fuse is not affected by the ambient temperature. When the fuse is used in an environment greater than 30℃, the ambient temperature has a great influence on the rated current carrying capacity of the fuse.

7. Melting characteristics of fuse-link:

Due to the presence of inductance or capacitance in the line, there is often a surge current at the moment of switching on and off the line. The inrush current may be 7-10 times the normal working current. The pulse width and waveform vary with the line. The surge current is in the circuit every time. Switch machine will appear, you need to choose a time delay fuse, depending on the degree of anti-surge, there is a difference between medium time delay (M), time delay (T) and long time delay (TT), sometimes in order to protect important components, such as Thyristor, IC, hope that when there is a fault current fuse, it will be opened quickly, then you should choose fast (F) fuse or (FF) fast fuse.

8. I2T value Joule integral