Resettable fuse - packaging process

Resettable fuse - packaging process(Metal Oxide Varistor)

Select modified epoxy resin polyethylene / carbon black self-recovery fuse packaging materials, and to study the impact of the package on the thermal characteristics of the fuse, the encapsulation layer affect the heat capacity of the core material, through current is large enough, the package fuse action time almost no effect, and when the through current is smaller, the encapsulation layer at 120 ° C (melting point of polyethylene) curing the fuse a certain gap exists between the encapsulation layer and the core material, the deterioration of cooling capacity of the core material, and the thermal expansion of the core material can be carried out smoothly, shorter operating time. Therefore, fuse encapsulated in the core material should reach a temperature of the maximum thermal expansion.

Resettable fuse - related issues

What fuse is it?

The fuse is also known as fuse, IEC127 standards will define it as "fuse (fuse-link). It is a mounting electrical components in the circuit, to ensure the safe operation of the circuit. The role of the fuse: circuit failure or abnormal, accompanied by rising current, and elevated current may damage some important devices in the circuit or expensive devices, and may even cause a fire burned circuit. Circuit correctly placed fuse, then the fuse will be in the current abnormally elevated to a certain height and a certain amount of time, their own fuse to cut off the current, which play the role of the safe operation of the protection circuit. Earliest fuse in Edison invented more than a century ago, is very precious, so initially it is used to protect expensive incandescent industrial technology developed incandescent.

The works fuse is what? (Metal Oxide Varistor)

All know, when the current flowing through the conductor, the conductor exists a certain resistance, the conductors will heat. And heat follow this formula: Q = 0.24I2RT; wherein Q is the amount of heat, and 0.24 is a constant, I is flowing through the conductor current, R is the resistance of the conductor, T is the current flowing through the conductor; so formula is not difficult to see a simple fuse works.

When the production of the fuse material and its shape is determined, the resistor R is determined relative to its temperature coefficient of resistance (if no consideration). When current flows through it, it will heat, its heat is also increasing with increasing time. The current and the size of the resistor determines the speed of generating heat, the fuse structure and its installation conditions to determine the rate of heat dissipation, and if the velocity is less than the speed of heat dissipation generated heat when the fuse is not blown. If the speed of heat is generated is equal to the speed of heat dissipation within quite a long time, it does not fuse. Produce heat speeds greater than the speed of heat dissipation, the heat generated will be more and more. Because it has a certain specific heat and mass, the increase in heat in the temperature rise on the fuse occurs when the temperature is raised to above the melting point of the fuse of the fuse. This is the fuse works. They should know from this principle in the design and manufacture of fuse must carefully study the physical characteristics of your chosen material, and to ensure that they are consistent geometry. Because of these factors on the fuse normal work since an important role. Similarly, when you use it, be sure to properly install it.

Fuse structure? What are the functions of each? What is required?

General fuse is composed of three parts: First, melt part, it is the core of the fuse, the blown play off the current role, the same class, the same specification fuse melts, the material has to be the same, the same geometric dimensions, the resistance value as small as possible and to be consistent, it is the most important is the fusing characteristics to be consistent; second electrode portion, there are usually two, which is the important member of the melt and a circuit coupled, it must have good electrical conductivity, should not produce significant the installation of contact resistance; bracket portion, a melt of the fuse are generally slender and soft, and the role of the stent is to melt fixed and three parts become rigid overall ease of installation, use, it must have good mechanical strength, insulating properties, heat resistance and flame retardancy, in use, should not produce fracture, deformation, phenomena such as combustion and short;

The fuse power circuits and high-power devices used, not only general fuse three parts, but also interrupter device, because of the type of fuse protection circuit is not only the work of current and when the melt blown two terminal voltage is also high, often melt has melted (fused) or even vaporized, but the current is not cut off, and the reason is that in fusing the moment in the role of the voltage and current, the fuse between the two electrodes pull arc phenomena. This interrupter device must have a strong insulation and good thermal conductivity, and is negatively charged. Quartz sand is the commonly used the interrupter material.

In addition, there are some fuse indication device, and its role is when the action fuse (fuse) after the occurrence of certain changes in appearance, easy maintenance staff found, for example: luminous, color, pop-up solid indicator. (Metal Oxide Varistor)