We all know that when the current flows through the conductor, because the conductor there is a certain resistance, so the conductor will heat. Q is the heat, 0.24 is a constant, I is the current flowing through the conductor, R is the resistance of the conductor, and T is the time that the current flows through the conductor. In this way, the heat is the same as the current, We can easily see the simple working principle of the fuse.
When the material and shape of the fuse are determined, the resistance R is relatively constant (if its resistance temperature coefficient is not taken into account). When the current flows through it, it will heat up, with the increase of time its heat is also increasing. The size of the current and the resistance determines the rate at which the heat is generated. The configuration of the fuse and the condition of its installation determine the rate of heat dissipation. If the velocity of heat is less than the rate of heat dissipation, the fuse will not blow. If the speed of heat generation is equal to the speed of heat dissipation, it will not blow for a long period of time. If the heat generated by the speed is greater than the speed of heat dissipation, then the heat will be more and more. And because it has a certain heat and quality, the increase in heat is reflected in the temperature rise, when the temperature rises above the fuse above the fuse when the fuse occurred. This is the working principle of the fuse. From this principle, you should know that when designing and manufacturing fuses, you must carefully study the physical properties of the materials you choose and ensure that they have consistent geometric dimensions. Because these factors on the fuse can work properly played a vital role. Likewise, when you use it, be sure to install it correctly.
The general fuse consists of three parts:
First, the melt part, it is the core of the fuse, when the fuse to cut off the role of current, the same type, the same specifications of the fuse melt, the same material, geometric dimensions to be the same, the resistance value as small as possible and consistent, The most important is the fuse characteristics to be consistent;
Second, the electrode part, usually two, it is an important part of the melt and circuit connection, it must have good conductivity, should not produce a significant installation contact resistance
Third, the bracket part, the fuse of the melt are generally slender and soft, the role of the bracket is to melt the fixed and make the three parts into a rigid overall easy to install, use, it must have good mechanical strength, insulation, heat Sexual and flame retardant, in use should not produce fracture, deformation, combustion and short circuit and so on;
Power circuits and high-power equipment used by the fuse, not only the general three parts of the fuse, but also the arc device, because the protection of such a fuse circuit is not only a large current, and when the melt occurs when the two The end of the voltage is also high, often the melt has melted (blow) or even vaporized, but the current is not cut off, the reason is in the moment of the fuse in the voltage and current under the action of the fuse between the two electrodes Arc phenomenon. The arc extinguishing device must have a strong insulation and good thermal conductivity, and was negative. Quartz sand is commonly used arc extinguishing materials.
In addition, there are some fuse fuse device, its role is when the fuse action (fuse) after its own appearance changes, easy to be found by maintenance personnel, such as: light, color, pop-up solid indicator.