Fuses are also known as current fuses, which IEC127 defines as "circuit-breakers". It is mainly an overload protection. When the fuse is properly installed in the circuit, the fuse will cut off the current and protect the circuit safe operation when the current anomaly rises to a certain height and heat.
Invented by Edison fuse is used to protect more than one hundred years ago when the expensive incandescent bulbs, along with the development of The Times, the fuse protection power equipment is not trained in current overheat damage, avoid electronic equipment serious damage caused by internal fault.
Invented by Edison fuse is used to protect more than one hundred years ago when the expensive incandescent bulbs, along with the development of The Times, the fuse protection electronics/electrical equipment not trained in current/overheating and avoid electronic equipment serious damage caused by internal fault.
When the current flows through a conductor, the conductor will heat up because of the resistance of the conductor. And the calorific value follows this equation: Q=0.24 I2RT; Q is heat, 0.24 is a constant, I is the current flowing through the conductor, R is the resistance of the conductor, T is the time when the current flows through the conductor; In accordance with this formula, it is not difficult to see the simple working principle of fuses.
When the material and its shape of the fuses are determined, its resistance R is relatively certain (unless its resistance temperature coefficient is considered). As the current flows through it, it heats up, increasing its heat as time increases. Current and resistance of size to determine the speed of heat, the structure of the fuse and its installation conditions to determine the speed of heat dissipation, if the speed is less than the speed of heat dissipation of heat, the fuse is not fuse. If the rate of heat produced is equal to the rate of heat dissipation, it will not be fused for a considerable amount of time. If the rate of heat is greater than the rate of heat dissipation, then more and more heat will be generated. Because it has certain specific heat and quality, its heat increase is reflected in the temperature rise, when the temperature rises to the fuse of the fuse, the fuse is blown out. That's how fuses work. We should know from this principle that you must carefully study the physical properties of your selected materials when designing the fuse, and ensure that they have a uniform geometric dimension. Because these factors are important for the safety of the fuse. Again, you must install it properly when you use it.
1. The normal working current under the condition of 25 ℃, the fuse current rating is usually reduced by 25% to avoid harmful fuse. Most traditional fuses have low melting temperatures. Therefore, this kind of fuse is sensitive to the change of environment temperature. Such as A current rating for 10 A fuse is usually not recommended at 25 ℃ ambient temperature at greater than 7.5 A run down.
2. The voltage rating of the voltage rating fuse must equal or exceed the effective circuit voltage. The general standard voltage rating series is 32V, 125V, 250V and 600V.
3. The resistance of the resistance fuse is not important in the whole circuit. Since there are only a few ohms in a fuse with a less than 1 amperage, the problem should be considered when adopting a fuse in a low voltage circuit. Most fuses are made from a positive temperature coefficient, so there are cold resistance and thermal resistance.
4. Ambient temperature fuse current carrying capacity, the experiment was conducted under the condition of 25 ℃ ambient temperature, this experiment is influenced by environmental temperature change. The higher the ambient temperature, the higher the working temperature of the fuse and the shorter life expectancy. Conversely, running at a lower temperature will prolong the fuse's lifespan.
5. The rated capacity is also known as the breaking capacity. The rated capacity of the fuse is the maximum permissible current that the fuse can actually fuse at the rated voltage. In short circuit, the fuse will be passed through the instantaneous overload current which is larger than the normal working current. Safety running requires the fuse to remain intact (no burst or rupture) and eliminate short circuit.