The same thing is that both can achieve short-circuit protection. The principle of a fuse is to use current to flow through the conductor, causing it to heat up. After reaching the melting point of the conductor, the conductor melts, so disconnecting the circuit protects the electrical appliances and circuits from being burned out. It is an accumulation of heat, so overload protection can also be achieved. Once the melt burns out, it needs to be replaced. A circuit breaker can also achieve short-circuit and overload protection for circuits, but the principle is different. It achieves circuit breaker protection through the bottom magnetic effect of the current (electromagnetic release), and overload protection through the thermal effect of the current (not fusing, and there is often no need to replace components). In practice, when the electrical load in the circuit approaches the load of the fuse used for a long time, the fuse will gradually heat up until it blows. As mentioned ab
Precautions for using fuses: 1. The protective characteristics of the fuse should be adapted to the overload characteristics of the protected object. Considering the possible short-circuit current, a fuse with corresponding breaking capacity should be selected; 2. The rated voltage of the fuse should adapt to the line voltage level, and the rated current of the fuse should be greater than or equal to the rated current of the melt; 3. The rated current of each level of fuse melt in the circuit should be matched accordingly, and the rated current of the previous level of melt must be greater than the rated current of the next level of melt; 4. The melt of the fuse should be matched according to the requirements, and it is not allowed to arbitrarily increase the melt or use other conductors to replace the melt. Inspection of fuses: 1. Check whether the rated values of fuses and melts match the protected equipment; 2. Check the appearance of the fuse for damage or deformation, a
In low-voltage distribution systems, fuses are a type of electrical appliance that plays a safety protection role. Fuses are widely used for power grid protection and electrical equipment protection. When a short circuit fault or overload occurs in the power grid or electrical equipment, they can automatically cut off the circuit to avoid damage to electrical equipment and prevent accidents from spreading. A fuse is composed of an insulation base (or support component), contacts, melt, etc. The melt is the main working part of the fuse. The melt is equivalent to a special section of wire connected in series in a circuit. When a short circuit or overload occurs in the circuit, the current is too high, and the melt melts due to overheating, thereby cutting off the circuit. Melts are often made into filaments, grids, or sheets. Melt materials have the characteristics of relatively low melting point, stable characteristics, and easy melting. Generally, lead-tin alloy, silver plated co
1. When protecting smooth loads without starting process, such as lighting circuits, resistors, electric furnaces, etc., the rated current of the melt is slightly greater than or equal to the rated current in the load circuit. 2. The melt current of a single motor that operates for a long time can be selected based on the maximum starting current or according to the following formula: IRN ≥ (1.5-2.5) IN In the formula, IRN - rated current of the melt; IN - Rated current of the motor. If the motor starts frequently, the coefficient in the formula can be appropriately increased to 3-3.5, depending on the actual situation. 3. Protecting multiple motors that have been operating for a long time (power supply main) IRN ≥ (1.5-2.5) IN max+ Σ IN IN max - The rated current of a single motor with the maximum capacity. Σ In other words, the sum of the rated current of the motor.
The fuse is mainly composed of three parts: the melt, the shell, and the support, among which the melt is a key component that controls the fusing characteristics. The material, size, and shape of the melt determine the fusing characteristics. Melt materials are divided into two categories: low melting point and high melting point. Low melting point materials such as lead and lead alloys have a low melting point and are prone to melting. Due to their high electrical resistivity, the cross-sectional size of the melt produced is larger, and the metal vapor generated during melting is more. They are only suitable for fuses with low breaking capacity. High melting point materials such as copper and silver have a high melting point and are not easy to fuse. However, due to their low electrical resistivity, they can be made into smaller cross-sectional sizes than low melting point melts. They produce less metal vapor during melting and are suitable for fuses with high breaking capacity.
Spiral fuse: There is a fuse indicator on the upper cover of the melt. Once the melt melts, the indicator immediately pops up and can be observed through the glass hole on the ceramic cap. It is commonly used in machine tool electrical control equipment. Spiral type fuse. The breaking current is large and can be used for short circuit protection in circuits with voltage levels of 500V and below, and current levels of 200A and below. Enclosed fuses: Enclosed fuses are divided into two types: filled fuses and unfilled fuses, as shown in Figures 3 and 4. Fuses with fillers are generally made of square porcelain tubes filled with quartz sand and melt, with strong breaking capacity. They are used in circuits with voltage levels below 500V and current levels below 1KA. The unfilled sealed fuse packs the melt into a sealed cylinder, with a slightly smaller breaking capacity, and is used in power grids or distribution equipment below 500V and 600A. Quick fuse: Quick fuse is mainly used f
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