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Joined: 9/14/2022(UTC) Posts: 25  Location: 广东
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As we all know, when electric current flows through a conductor, the conductor will heat up because there is a certain resistance. And calorific value follows this formula: Q= 0.24i2RT; Where Q is the 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 of the current flowing through the conductor; According to this formula, it is not difficult to see the simple working principle of the thermal fuse.
When the material and shape of the thermal fuse are determined, its resistance R is relatively determined (if its resistance temperature coefficient is not considered). When an electric current flows through it, it heats up, and its heat increases over time. The size of the current and resistance determine the speed of heat generation, and the structure of the thermal fuse and its installation determine the speed of heat dissipation. If the speed of heat generation is less than the speed of heat dissipation, the thermal fuse will not be blown. If the rate of heat generation is equal to the rate of heat dissipation, it will not fuse for a long time. If the rate at which heat is produced is greater than the rate at which it is dissipated, more and more heat will be produced. Because it has certain specific heat and mass again, the increase of its quantity of heat is displayed on the rise of temperature, when the temperature rises to the melting point above of hot fuse, hot fuse produced fuse break. This is how a thermal fuse works. You should know from this principle that you must carefully study the physical properties of your chosen materials when designing and manufacturing thermal fuses and ensure that they have consistent geometric dimensions. These factors play an important role in the normal operation of the thermal fuse. Again, make sure you install it correctly when you use it.
What is the construction of the thermal fuse? What effect does each have? What are your requirements?
A general fuse consists of three parts:
One is the melt part, which is the core of the thermal fuse and plays the role of cutting off the current when the fuse is broken. The melt of the same type and specification of the thermal fuse should have the same material, the same geometric size, the resistance value should be as small and consistent as possible, and the most important thing is the fuse characteristics should be consistent.
Two is the electrode part, usually there are two, it is an important part of the melt and the circuit connection, it must have good electrical conductivity, should not produce obvious installation contact resistance;
Part three is stents, thermal fuse melts is generally fine soft, the role of stents is to melt and make three parts fixed rigid overall ease of installation, use, it must have good mechanical strength, insulation, heat resistance and flame retardant, in use should not produce the phenomenon such as fracture, deformation, combustion and short circuit;
Power circuit and power equipment used by the fuse, not only has the three sections of the general fuse, and arcing device, not only because this kind of fuse protection circuit working current is larger, and when the melt occurs when the voltage at the ends of the fuse is very high, often appear the melt has melted (fuse) have even vaporizing, but current is not cut off, The reason is that under the action of voltage and current at the moment of fusing, the phenomenon of arc pulling occurs between two electrodes of the fuse. The arc extinguishing device must have strong insulation and good thermal conductivity, and be electronegative. Quartz sand is a commonly used arc extinguishing material.
In addition, there are some fuses have fuse indicating 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 change, pop up solid indicator, etc..
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