1. Introduction of fuse
Characteristics and use of fuses are based on the current exceed the specified value for a period of time, with its own generated heat to melt the melt, so that the circuit is broken; using this principle made of a current protector. Fuse is widely used in high and low voltage distribution systems and control systems and electrical equipment, as a short circuit and overcurrent protector is one of the most commonly used protection devices.
Fuse is a kind of over-current protector. The Characteristics and use of fuses are mainly composed of fuse and fuse tubes and additional filler and other parts. When used, the fuse is connected in series in the protected circuit, when the current of the protected circuit exceeds the specified value, and after a certain period of time, the heat generated by the fuse itself melts the fuse, so that the circuit is broken, thus playing the role of protection. When the overload or short-circuit current passes through the fuse, the fuse itself will heat up and fuse off, thus playing a certain protective role for the electric power system, various electrical equipment, and household appliances. When the overload current is small, the fusing time is long; when the overload current is large, the fusing time is short. Therefore, in a certain overload current range until the current returns to normal, the fuse will not fuse, can continue to use. The fuse is mainly composed of 3 parts: fuse, shell, and standoff, of which the fuse is the key component to control the fusing characteristics.
2. Fuse characteristics
1. fuse material is divided into two categories: low melting point and high melting point. Low melting point materials such as lead and lead alloy, its low melting point is easy to fuse, due to its greater resistivity, so the cross-sectional size of the melt is made larger, fusing metal vapor generated more, only for a low breaking capacity of the fuse. High melting point materials such as copper, silver, its high melting point, not easy to fuse, but because of its low resistivity, can be made into a smaller cross-sectional size than the low melting point fuse, fusing metal vapor generated less, suitable for a high breaking capacity of the fuse. The shape of the fuse is divided into two types: filamentary and ribbon. Change the shape of the variable cross-section can significantly change the fusing characteristics of the fuse. 3. fuse has inverse time-delay characteristics, that is, when the overload current is small, the fusing time is long; when the overload current is large, the fusing time is short. Therefore, in a certain range of overload current, when the current returns to normal, the fuse will not fuse, can continue to use. Fuse has a variety of different fusing characteristics curves, can be applied to the needs of different types of protection objects. 4. fuse installed in the circuit to ensure the safe operation of the circuit electrical components. When a fault or abnormality occurs in the circuit, accompanied by a rising current, and the rising current may damage some important devices or valuable devices in the circuit, or may burn the circuit or even cause a fire. If the circuit is correctly placed in the fuse, then the fuse will be abnormally high in the current to a certain height and at a certain time, its own fuse cut off the current, thus playing a role in protecting the safe operation of the circuit. The fuse cuts off the current, thus playing a role in protecting the safe operation of the circuit.
3. The use of fuse precautions
① fuse protection characteristics should be compatible with the overload characteristics of the protected object, taking into account the possible short-circuit current, choose the corresponding breaking capacity of the fuse.
② fuse rated voltage to adapt to the line voltage level, the rated current of the fuse should be greater than or equal to the rated current of the fuse.
③ line at all levels of a fuse rated current to match, keep the previous level fuse rated current must be greater than the next level fuse rated current.
④ The fuse of the fuse should be used in accordance with the requirements of the matching fuse, not allowed to arbitrarily increase the fuse or replace the fuse with other conductors.
4. Fuse fusing causes
1. short circuit fault or overload operation and normal fusing. 2. fuse use too long, fuse due to oxidation or high temperature in operation so that the fuse characteristics change and false break. 3. fuse installation mechanical damage, so that its cross-sectional area becomes small and causes a false break-in operation.
5. Replace the fuse
1. before installing a new fuse, Characteristics, and use of fuses are used to find out the cause of the fuse meltdown, not to determine the cause of the fuse, do not remove the fuse test delivery. 2. when replacing the new fuse, check whether the fuse rating and the protected equipment match. 3. when replacing the new fuse, to check the internal burn of the fuse tube, such as serious burns, the fuse should be replaced at the same time. When the porcelain fuse tube is damaged, it is not allowed to replace the tube with other materials. When replacing the fuse with filler type fuse, pay attention to filler.