Technical Parameters of Low-voltage Fuses

1. Rated Voltage

2. Rated Current

3. Protective Characteristic

The time-current characteristic, also known as I-t characteristic or protective characteristic, is referred to as the ampere-second characteristic of a fuse. It describes the relationship curve between the current flowing through the fuse element and the melting time under specified conditions. The I-t curve shows that the melting time of the fuse shortens as the current rises, presenting an inverse time characteristic.

On the I-t characteristic curve lies a boundary between melting current and non-melting current. The corresponding current is defined as the minimum melting current (or critical current), denoted as IRmin. Generally, the minimum melting current refers to the minimum current that can melt the fuse within 1~2 hours. Per fuse design requirements, the fuse element must not melt at rated current INN, so IRmin shall be greater than INN.

4. Rated Breaking Capacity

It refers to the prospective short-circuit current that a fuse can reliably interrupt under specified operating conditions, namely the maximum current the fuse can break.

When a short circuit occurs in the circuit, the short-circuit current will be cut off after a short period. If the fuse operates before the short-circuit current reaches its peak value, the fuse will exert a current-limiting effect. Therefore, a stronger current-limiting effect corresponds to a higher breaking capacity.

Operating Principle of Low-voltage Fuses

In case of circuit overload or short-circuit fault, if the current through the fuse reaches or exceeds a certain threshold, heat generated by the fuse element will raise its temperature to the melting point of the metal material. The fuse element melts automatically to disconnect the fault current and realize circuit protection.