Fuses are commonly known as fuses or fuse tubes.The first fuse was invented by Edison more than 100 years ago. At that time, due to the underdeveloped industrial technology, incandescent lamp was very expensive, so it was originally used as a fuse to protect the expensive incandescent lamp.

　　Fuses protect electronic equipment from damage by current and avoid serious damage caused by internal faults.

　　Therefore, each fuse has a rated specification, and when the current exceeds the rated specification, the fuse will blow.When a current between the conventional non-fusing current and the rated breaking capacity (current) specified in the relevant standard is applied to the fuse, the fuse shall work satisfactorily without endangering the surrounding environment.

　　The expected fault current of the circuit installed by the fuse must be less than the rated breaking capacity current specified in the standard, otherwise, when the fault occurs, the fuse will appear continuous arc, ignition, fuse burning, melting together with the contact parts, fuse mark cannot be recognized and other phenomena.Of course, the breaking ability of inferior fuse can not meet the requirements of the standard.

　　In addition to fusing resistors, there are common fuses, thermal fuses and self-restoring fuses.The protection element is generally connected in series in the circuit, it appears in the circuit over current, over voltage or overheating and other abnormal phenomena, will immediately fuse and play a protective role, can prevent further expansion of the fault.

　　(1) ordinary fuse

　　Common fuse is commonly known as fuse or fuse tube, which belongs to the fusing type of non-restorable fuse, and can only be replaced with a new fuse after fusing.It is represented by "F" or "FU" in the circuit.

　　Structural characteristics of common fuses

　　A common fuse usually consists of a glass tube, a metal cap and a fuse.The two metal caps are covered on both ends of the glass tube, and the fuse (made of low-melting metal material) is installed in the glass tube. The two ends are welded on the central hole of the two metal caps respectively.When using the fuse into the safety seat, and the circuit can be in series.

　　Fuse fuse is mostly straight, only color television, computer monitors used in the delay fuse is spiral fuse.

　　Main parameters of ordinary fuse

　　The main parameters of ordinary fuse are rated current, rated voltage, ambient temperature and reaction speed.Rated current, also known as breaking capacity, refers to the current value of the fuse at the rated voltage.The normal operating current of the fuse is less than 30% of the rated current.The rated current value of domestic fuse is usually marked on the metal cap, while the imported fuse is marked on the glass tube with color ring.

　　Rated voltage refers to the most adjustable fuse voltage, it is 32V, 125V, 250V and 600V four specifications.The actual operating voltage of the fuse should be lower than or equal to the rated voltage value.If the operating voltage value of the fuse exceeds the rated voltage value, it will fuse quickly.

　　The current carrying capacity of the fuse was tested at 25℃.The service life of fuse is inversely proportional to the working environment temperature.The higher the ambient temperature, the higher the operating temperature and the shorter the service life of the fuse.

　　Response rate refers to how quickly the fuse responds to various electrical loads.Fuses can be classified into normal response type, delay disconnect type, fast action type and current limiting type according to the reaction speed and performance.

　　(2) thermal fuse

　　Thermal fuse, also known as temperature fuse, is a kind of non-recoverable overheating insurance element, widely used in various electric cooker, electric motor, washing machine, electric fan, power transformer and other electronic products.Thermal fuses can be divided into low-melting alloy type thermal fuses, organic compound type thermal fuses and plastic-metal type thermal fuses.

　　Low melting alloy type hot fuse

　　The heat-sensitive body of low-melting alloy type thermal fuse is made of alloy material with fixed melting point.When the temperature reaches the melting point of the alloy, the temperature sensitive body will automatically fuse and be disconnected by the protective circuit.According to its different structure, low-melting alloy type thermal low-melting alloy type thermal fuse can be divided into three types: gravity type, surface tension type and spring reaction type.

　　Organic compound type thermal fuse

　　Organic compound type thermal fuse consists of temperature sensing body, movable electrode and spring.Thermosensitive body is made of organic compounds with high purity and low melting temperature range.Normally, the movable electrode contacts the fixed end point, and the circuit is connected by the fuse.When the temperature reaches the melting point, the temperature sensitive body will automatically fuse, and the movable electrode will be disconnected from the fixed endpoint under the action of the spring, which will disconnect the circuit for protection.

　　Plastic-metal type hot fuse

　　The plastic-metal thermal fuse adopts the surface tension structure, and the resistance value of the temperature sensitive body is almost 0.When the operating temperature reaches the set temperature, the resistance value of the temperature sensitive body will suddenly increase, preventing the current from passing through.

　　(3) self-restoring fuse

　　Self-restoring fuse is a new type of safety element with over current and over heat protection function, which can be used repeatedly.

　　The structural principle of self - restoring fuse

　　The self-restoring fuse is a PTC thermal sensor with positive temperature coefficient, which is made of polymer and conductive material, etc. It is in series in the circuit, and can replace the traditional fuse.

　　When the circuit is working normally, the self-restoring fuse is in the on state.When the circuit overcurrent fault occurs, the temperature of the fuse itself will rise rapidly. When the polymer material is heated, it will quickly enter the state of high resistance. The current in the circuit will be cut off and the circuit will enter the state of protection.When the fault disappears and the self-restoring fuse cools down, it will turn on the circuit automatically with low resistance.

　　The operating speed of the self-restoring fuse is related to the abnormal current and the ambient temperature. The higher the current and the higher the temperature, the faster the operating speed will be.

　　Commonly used self - restoring fuse

　　Self - restoring fuse has plug-in type, surface - mounted type, chip type and other structural shapes.Commonly used plug-in self-restoring fuses are RGE series, RXE series, RUE series, RUSR series, etc., which are used for computers and general electrical appliances.

You May Like: