73 views Yuda Electronic (HK) Technology Co.,Limited. 2019-06-14
The fuse is a fusible line, which is the oldest and most commonly used overload protection method.
Modern fuse technology is an evolving technology, and better new fuses are constantly being developed to meet the more demanding requirements of protecting semiconductor circuits. In order to obtain the most reliable long-term performance and the best protection, you must choose the fuse that is suitable for use.
From the electrical point of view, the main three parameters of the fuse classification: rated current, rated voltage, rated melting heat energy value I2t.
It is common knowledge that a fuse has a current rating that must be greater than the maximum DC current or current rms value of the circuit being protected. There are two other equally important ratings for the correct fuse selection.
The rated voltage of the fuse is not necessarily related to the input voltage. The voltage across the fuse depends on the input voltage and the type of circuit. For example, at the instant of a blow, the voltage on the fuse in series with the inductive circuit may be several times the supply voltage.
Improper selection of the rated voltage of the fuse can cause excessive current in the event of a fault. In several special cases, the fuse box may explode, posing a fire hazard. Special methods are used in high-voltage fuses, including filling fine sand and loading the fuses with springs.
Rated thermal energy value I2t
This characteristic of the fuse is defined by the energy that must be dissipated to melt the fuse. To melt the fuse, the heat generated on the component must be faster than the rate at which it conducts heat, which requires a deterministic current to time product.
In a short period of time, usually less than 10 ms, very little heat can be conducted out of the fuse and the energy necessary to melt the fuse is a function of the specific heat, mass and alloy type of the fuse. For a particular fuse, the heat consumed by the fuse is in the form of W·s(J), or I2R*t. The fuse resistance is constant, and the heat is proportional to I2t. For a particular fuse, the arc energy is called the heat value of fusion I2t.
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