Composition Of Fuses

Basic composition
A general fuse consists of three parts: the first is the melt part, which is the core of the fuse and plays a role in cutting off the current when it melts. Fuses of the same type and specification should have the same material, geometric dimensions, and resistance values as small and consistent as possible. The most important thing is to have consistent melting characteristics. Household fuses are commonly made of lead antimony alloy; The second is the electrode part, which usually has two important components that are connected between the melt and the circuit. It must have good conductivity and should not produce obvious installation contact resistance; The third part is the bracket. The melt of the fuse is generally thin and soft, and the function of the bracket is to fix the melt and make the three parts a rigid whole for easy installation and use. It must have good mechanical strength, insulation, heat resistance, and flame retardancy, and should not produce phenomena such as breakage, deformation, combustion, and short circuit during use.
Arc extinguishing device
The fuses used in power circuits and high-power equipment not only have the three parts of a general fuse, but also have an arc extinguishing device. This type of fuse not only protects the circuit with a high working current, but also has a high voltage at both ends when the melt melts. Often, the melt has melted (melted) or even vaporized, but the current is not cut off. The reason is that at the moment of melting, under the action of voltage and current, an arc pulling phenomenon occurs between the two electrodes of the fuse. This arc extinguishing device must have strong insulation and good thermal conductivity, and be negatively charged. Quartz sand is a commonly used arc extinguishing material.
Fusing device
In addition, some fuses have a blown indicator device, which is used to indicate that when the fuse is activated (blown), it undergoes a certain appearance change and is easily detected by maintenance personnel, such as emitting light, changing color, and popping solid indicators.
Breaking capacity
Broadcast
edit
When a current between the conventional non fusing current and the rated breaking capacity specified in relevant standards acts on a fuse, the fuse should be able to operate satisfactorily without endangering the surrounding environment. The expected fault current of the circuit in which the fuse is installed must be less than the rated breaking capacity current specified in the standard. Otherwise, when the fuse blows, continuous arcing, ignition, fuse burning, melting together with the contact parts, and unrecognizable fuse markings may occur. Of course, the breaking capacity of low-quality fuses does not meet the standard requirements, and the above-mentioned hazards can also occur during use. [2]
classification
According to the protection form, it can be divided into overcurrent protection and overheating protection. The fuse used for overcurrent protection is commonly referred to as a fuse (also known as a current limiting fuse). The fuse used for overheating protection is generally referred to as a "temperature fuse". Temperature fuses are divided into low melting point alloy, temperature sensing trigger, memory alloy, and so on. Temperature fuses are used to protect heating appliances or easily heating appliances from excessive temperature, such as hair dryers, electric irons, rice cookers, electric furnaces, transformers, motors, etc. They respond to the increase in temperature of electrical appliances and do not care about the working current of the circuit. Their working principle is different from "current limiting fuses".
According to the scope of use, it can be divided into: power fuse, machine tool fuse, electrical instrument fuse (electronic fuse), and automotive fuse.
According to body integration, it can be divided into: large, medium, small, and micro. According to the rated voltage, it can be divided into: high-voltage fuse, low-voltage fuse, and safety voltage fuse.
According to the breaking capacity, it can be divided into high and low breaking capacity fuses.
According to shape, it can be divided into: flat headed tubular fuses (also divided into internal and external welded fuses), pointed tubular fuses, blade type fuses, spiral type fuses, plug-in type fuses, flat type fuses, wrapped type fuses, and patch type fuses.
According to the melting speed, it can be divided into: extra slow fuse (generally represented by TT), slow fuse (generally represented by T), medium speed fuse (generally represented by M), fast fuse (generally represented by F), and extra fast fuse (generally represented by FF).
According to the standard classification, it can be divided into European standard fuses, American standard fuses, and Japanese standard fuses.
According to type, it can be divided into: current fuse (patch fuse, micro fuse, plug-in fuse, tubular fuse), temperature fuse (RH [square type], RP [resistance type], RY [metal shell]), and self recovery fuse (plug-in, stacked, patch).
According to size, it can be divided into: SMT type 06030805120612181220162920; Non SMT type: 2.4 × 7, 3 × 7, 3.6 × 10, 4.5 × 15, 5.0 × 20, 5.16 × 20, 6 × 25, 6 × 30, 32, 8.5 × 8, 8.5 × 8, 38, 14 × 51.
Resettable fuse
Low zero power resistance: The self resetting fuse has a low impedance, low power loss during normal operation, and low surface temperature.
Fast overcurrent protection speed: Due to its material characteristics, the self resetting fuse has a much faster response speed to overcurrent state than other overcurrent protection devices.
Self locking operation: The self resetting fuse is in the overcurrent protection state, locked in the high resistance state with a very small current, and will only restore the low resistance state after cutting off the power or the overcurrent disappears.
Automatic reset: After providing overcurrent protection (troubleshooting), the self resetting fuse resets itself without the need for replacement.
High current resistance: Self resetting fuses have excellent resistance to high current, and some specifications can withstand 100A current shocks.
Application: PPTC has a wide range of applications and can be used in various electronic products, communication products, power supplies, etc.