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I. Introduction
Name: Fuse (fuse) is also known as current fuse.
Fuse (fuse) is also known as current fuse, IEC127 standard defines it as ‘fuse (fuse-link)’. A pcb board fuse is a wire made of a silver-copper alloy with a relatively high resistivity and a low melting point. If a fuse is correctly placed in a circuit, it will cut off the current when the current rises abnormally to a certain height and heat, thus protecting the circuit. More than a hundred years ago by Edison invented the fuse used to protect the then expensive incandescent lamps, with the development of the times, the fuse to protect electronic/electrical equipment from overcurrent/overheating, to avoid electronic equipment due to internal failure caused by serious injury.
Role: It mainly acts as an overload protection. Properly placed in the circuit, when the current or temperature rises abnormally to a certain limit, the fuse will blow the fuse and cut off the current, thus protecting the whole circuit.
Application direction: fuse and fuse belong to the same safety devices, play the same role, are used to protect the safety of the entire line, the fuse is mainly used for weak products, such as chargers, power adapters, etc., while the fuse is used for charging cabinets, photovoltaic energy and other products.
Second, the principle of work
When the current flows through the conductor, because there is a certain resistance of the conductor, so the conductor will heat. And the amount of heat follows the formula: Q = 0.24 I2RT
where Q is the amount of heat, 0.24 is a constant, I is the current flowing through the conductor, R is the resistance of the conductor, T is the current flowing through the conductor time; according to this formula, we are not difficult to see the simple principle of the work of the fuse.
At high overloads, a slow blow fuse operates on the same principle as a pcb board fuse because there is no time to start the diffusion process.
- High overloads are defined as overload currents of 4 In and higher.
-Spreading starts at 150-170°C. Slow blow fuses should not be operated above 150°C for long periods of time to prevent deterioration.
-Although there is no solder ball / plating, fast acting fuses are not permitted to be used above 175-225°C for long periods of time.
- Oxidation of the fuse material.
- Oxidation of the fuse material. Change of material properties.
Third, the basic structure of
general fuse consists of three parts: one is the melt part, it is the core of the fuse, when the fuse to play the role of cutting off the current, the same type, the same specification fuse melt, the material should be the same, the same geometric dimensions, the resistance value of as small as possible and to be consistent, and the most important is the same characteristics of the melting; two is the electrode part, it is the melt and the circuit is an important part of the linkage, it must have good conductivity, should not produce a significant change in the conductivity of the fuse. Conductivity, should not produce obvious installation contact resistance; Third, the bracket part, the fuse is generally slim and soft melt, the role of the bracket is to fix the melt and make the three parts of the rigid whole for easy installation, use, it must have good mechanical strength, insulation, heat resistance and flame retardant, should not produce fracture, deformation, combustion, and short-circuit and other phenomena in the use of the phenomenon.
-UMF * (Universal Modular Fuse).
-The first IEC and UL standard universal fuse
Surface mount and perforated fuse
Confirmation of electrical characteristics: F (fast blow), T (slow blow), self-recovery, here you need to combine the product with the actual application environment for the selection of the product, including surge (lightning strike) immunity Surge, the input inrush current of the relevant indicators. Specifically can be combined with the fuse specifications of the current and time curve for selection, the general switching power supply in the fuse for the slow-melting type. (Reminder: need to focus on whether the single pulse energy is less than the single pulse energy of the fuse)
-Slow blow: (time-delay type, anti-surge)
- Fuses act slowly at high overcurrents.
- The fuse is marked T.
- Slow blow fuses contain solder balls or plating.
-Slow blow fuses contain a tin ball or plating.
Fuses labelled F. -Fast acting. -Fast acting.
-Fuses are labelled F.
Verify Operating Temperature Range: The actual product application temperature range. The operating temperature range of the fuse should not be less than the actual product application temperature range.
Confirmation of package: Choose the most suitable fuse in combination with the size of the product, process, safety distance, cost, and so on. In particular, the electrical clearance and creepage distance before and after the fuse need to meet the basic insulation.
PCB board notes: products that need to do certification, you need to print the specifications of the fuse (rated operating voltage and rated operating current) on the PCB, products without certification requirements, it is best to synchronise the above as well.