What is a fuse and what does it do?
fuse is also known as a fuse, IEC127 standard defines it as "fuse-link". It is an electrical component installed in a circuit to ensure the safe operation of the circuit. The function of fuse is: when the circuit is faulty or abnormal, the current is constantly rising, and the rising current may damage some important or valuable components in the circuit, may burn the circuit or even cause a fire. If the circuit is correctly placed in the fuse, then the fuse will abnormally rise to a certain height and a certain time, its own fuse to cut off the current, so as to protect the safe operation of the circuit. The first fuse was invented by Edison more than a hundred years ago, and was originally used to protect expensive incandescent bulbs, which were expensive because of the lack of industrial technology at the time.
How does a fuse work?
We all know that when an electric current flows through a conductor, the conductor will heat up because it has some resistance. The calorific value follows this formula: Q=0.24I2RT; Where Q is the calorific value, 0.24 is a constant, I is the current flowing through the conductor, R is the resistance of the conductor, and T is the time the current flows through the conductor. According to this formula, we can see the simple working principle of the fuse.
When the material and shape of the fuse are determined, its resistance R is relatively determined (regardless of its resistance temperature coefficient). When an electric current flows through it, it heats up, increasing its calorific value over time. The size of the current and resistance determines the speed of heat generation, and the structure of the fuse and its installation determines the speed of heat dissipation. If the speed of heat generation is less than the speed of heat dissipation, the fuse will not blow. If the rate at which heat is generated is equal to the rate at which heat is dissipated, it will not be fused for quite a long time. If the rate at which heat is produced is greater than the rate at which heat is dissipated, more and more heat is produced. And because it has a certain specific heat and mass, the increase of its heat is reflected in the rise of temperature, when the temperature rises above the melting point of the fuse fuse will be blown. That's how a fuse works. We should know from this principle that you must carefully study the physical properties of the materials you choose when designing and manufacturing fuses and ensure that they have consistent geometric dimensions. Because these factors play an important role in the normal operation of the fuse. Again, when you use it, be sure to install it correctly.
What is the construction of the fuse? What are the effects of each? What are your requirements?
General fuse consists of three parts: one is the melt part, it is the core of the fuse, fuse to cut off the current role, the same type, the same specification of fuse melt, the material should be the same, the geometric size should be the same, the resistance value as small as possible and should be consistent, the most important is the fuse characteristics should be consistent; The second is the electrode part, usually there are two, it is an important part of the melt and the circuit connection, it must have good conductivity, should not produce obvious installation contact resistance; Three is the bracket part, fuse fuse melt is generally fine and soft, the role of the bracket is to fix the melt and make the three parts into a rigid whole easy to install, use, it must have good mechanical strength, insulation, heat resistance and flame retardant, in use should not produce fracture, deformation, combustion and short circuit phenomenon;
Power circuits and high-power equipment used by the fuse, not only general fuse three parts, but also arc extinguishing device, because this kind of fuse protection circuit not only the working current is larger, and when the melt is fusible the voltage at both ends is also very high, often appear melt has been melted (fusible) or even vaporized, but the current has not been cut off, The reason is that at the moment of fusing under the action of voltage and current, the two electrodes of the fuse arc phenomenon. The arc extinguishing device must have strong insulation and good thermal conductivity, and be negative. Quartz sand is commonly used as an arc extinguishing material.
In addition, there are some fuse indicating device, its role is when the fuse action (blown) after its appearance changes, easy to be found by maintenance personnel, such as: light, color, pop up solid indicator.
What kinds of fuses are there?
According to the protection form, can be divided into: over current protection and overheating protection. A fuse used for overcurrent protection is commonly referred to as a fuse (also called a current-limiting fuse). Fuses used for overheating protection are commonly referred to as "temperature fuses". Temperature fuse is divided into low melting point alloy shape and temperature trigger shape and memory alloy shape and so on (temperature fuse is to prevent heating appliances or easy heating appliances temperature is too high and protect, such as: hair dryer, electric iron, electric cooker, electric furnace, transformer, motor and so on; It responds to the temperature rise of electrical appliances, regardless of the working current of the circuit. It works differently from a "current-limiting fuse").
According to the scope of use, it can be divided into: power fuse, machine tool fuse, electrical instrument fuse (electronic fuse), automobile fuse.
According to the volume points, can be divided into: large, medium, small and micro.
According to the rated voltage, can be divided into: high voltage fuse, low voltage fuse and safety voltage fuse.
According to breaking capacity, can be divided into: high, low breaking capacity fuse.
By shape, they can be divided into: flat tubular fuse (which can also be divided into inner and outer welded fuse), pointed tubular fuse, guillotine fuse, spiral fuse, insert fuse, plate fuse, wrap fuse, and sticker fuse.
According to the fusing 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), extra fast fuse (generally represented by FF).
According to the standard points, can be divided into: European fuses, American fuses, Japanese fuses.