Current fuse parameters

1. Rated current

The nominal working current of the fuse, also known as In, is determined by the manufacturing department under laboratory conditions. Rated current values usually include 100mA, 200mA, 315mA, 400mA, 500mA, 630mA, 800mA, 1A, 1.6a, 2A, 2.5a, 3.15a, 4A, 5A, 6.3a, etc. However, companies usually provide rated current values for various fuses depending on customer requirements and actual use.

2. Rated voltage

The nominal working voltage of the fuse is Un, and the standard rated voltage of the general fuse is 32V, 60V, 125V, 250V, 300V, 500V and 600V. The fuse may be used at a voltage not greater than its rated voltage, but it is generally not permitted in a circuit with a voltage greater than the fuse's rated voltage.

3. Voltage drop

When the fuse reaches thermal equilibrium, that is, when the temperature is stable, the voltage measured at both ends of the fuse is called Ud. The voltage drop at both ends of the fuse affects the circuit and is specified in European regulations.

4. Fuse resistance

Usually divided into cold resistance and heat resistance, cold resistance is under the condition of 25 ℃ fusing, through the test current is less than 10% of the rated current measured by the resistance. The thermal resistance is converted by the voltage drop measured with rated current as the test current, and the calculation formula is R heat = Ud/In. Generally, the thermal resistance is greater than the cold resistance, and the fuse resistance value provided by our company is the cold resistance value, which is only used as a reference.

5. Overload current

Overload current is the current flowing through a circuit that is operating above normal. If the overload current cannot be cut off in time, other devices in the circuit may be damaged. Short circuit current refers to the current generated by partial or total short circuit in the circuit. Short circuit current is usually very large and is greater than the overload current.

6. Melting characteristics

This is the time/current characteristic (also known as ampere-second characteristic). There are usually two ways of saying it, i.e. I-t charts and test reports. The i-t graph is a curve formed by connecting the average fusing time coordinate of the fuse under different current loads in the coordinate system with the load current to the x coordinate and the fusing time to the y coordinate. Each type of fuse has a corresponding curve representing its fusing characteristics. The curve can be used to select a fuse. A test report is a record of test data for tests conducted according to standard requirements. Our i-t chart and test report are based on the data measured under experimental conditions, and the curves or test reports will differ under actual conditions. Therefore, the test report and i-t chart provided by our company are for reference only.

7. Ability to break

Also known as rated short circuit capacity, the maximum current at which the fuse can be safely disconnected at the rated voltage (ac is the effective value). It is an important safety pointer to a fuse. The code name for cracking ability is Ir.

Melting thermal value

In other words, the energy required to melt the fuse, codename I t, reads A2Sec. When the fuse disconnects in 8ms or less, it is the product of current and fuse time squared. It is a constant for each different type of fuse assembly. It is the parameter of the fuse itself, which is determined by the design of the fuse.

9. Temperature rise

Temperature rise refers to the difference between the fuse temperature when the temperature reaches stability under the condition that the current value of the fuse is set at 100% In and 115% In. In daily adjustment (UL).