Classification of miniature fuses for FBelec
â‘ The product can be divided into block type micro fuse and cylindrical type micro fuse according to the shape. The dimensions are 8 * 8 * 4mm, 8.5 * 8mm and 8.5 * 8 * 4mm respectively; The current range is from 50ma-6.3a to 125V / 250V;; Models include: AR5 AP5 AMF AF 372 382 370 392 2000 2010 MEF met MSF MST, etc
â‘¡ According to the fusing performance, micro fuse can be divided into fast fusing and slow fusing.
â‘¢ According to the standard, it can be divided into American regulations and European regulations, and the certification includes: UL VDE Semko cul CCC EK PSE, etc
Specification editing and broadcasting
Most miniature fuses have obtained ul248-14 certification of American national safety specification, which stipulates the following contents:
â‘ Power on capacity: power on according to the rated current for 1 hour without fusing.
② Temperature rise: the temperature rise when energized according to the rated current is less than 75 ℃.
â‘¢ Fuse test: fuse within 1 minute under the condition of 2 times of rated current.
â‘£ Breaking capacity: when the rated breaking capacity is added, there will be no continuous arcing or ignition.
Shape and structure editing and broadcasting
The shape of micro fuse can be divided into lead type and sheet type. If it is divided according to the structure of fuse element, it can be divided into linear and film type.
Select method to edit broadcast
In practical applications, it is not enough to select fuses only according to UL specifications.
1. Several problems that must be considered in selection
On the basis of understanding the parameters of the circuit used, the fuse is selected according to the following aspects: normal current, fusing current (current and time to fuse), open circuit voltage, short-circuit current, impulse current (current, time and times not cut off), and ambient temperature.
â‘ Normal current: first of all, we must know the normal current flowing through the fuse in the circuit used. Usually, we need to set a derating amount in advance, and then choose according to the following principle: that is, the normal current must be less than the product of rated current and derating coefficient.
â‘¡ Fusing current: according to UL specification, the fuse shall fuse quickly at twice the rated current. However, in most cases, in order to ensure reliable fusing, we recommend that the fusing current should be greater than 2.5 times the rated current. In addition, if the fusing time is important, it must also refer to the fusing characteristic diagram provided by the manufacturer for judgment.
â‘¢ Open circuit voltage: the open circuit voltage shall generally be selected to be less than the rated voltage. For example, when a fuse with a rated voltage of DC24V is used in an AC100V circuit, it may ignite the fuse or break the fuse.
â‘£ Short circuit current: we call the maximum current flowing when the circuit is short circuited as short circuit current. For various fuses, the rated breaking capacity is specified. When selecting fuses, we must pay attention not to make the short-circuit current exceed the rated breaking capacity. If a fuse with small breaking capacity is selected, it may break the fuse or cause a fire.
⑤ Impulse current: observe the waveform of impulse current (pulse current waveform) and calculate its energy with i2t value (Joule integral value). The impact on the fuse is also different with the size and times of impulse current. The ratio of i2t value of impulse current to i2t value of single pulse fusing determines the times that the fuse can withstand impulse current.
2. Other issues needing attention
In actual use, the special requirements and problems of Miniature Fuse on installation conditions, chemical resistance, ultrasonic cleaning resistance and other aspects must be confirmed by the manufacturer in advance.
Micro fuse is different from ordinary electronic components such as chip resistor and chip capacitor. Due to the differences of manufacturers, its specifications are quite different. In addition, the actual installation will have a certain impact on the heat dissipation of printed board and wiring. Therefore, whether the selection of micro fuse is correct or not should be determined by the state of the product.
NINGBO FBELE ELECTRONICS CO.,LTD.
FBELE company was founded in 1997, is China's leading manufacturer of acoustic and other electronic components, we designs,manufactures, distributes high quality products in very competitive price, bestservice, timely delivery, small order acceptable, etc. Our products include piezo ceramic element, piezoelectric buzzer, magnetic buzzer,speakers, transducer, receiver, electret condenser microphone, magnetic contact. Piezoelectric alarm,ultrasonic sensor,PZT ceramics,etc.
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