The functions of fuses: 1. Under normal circumstances, fuses play the role of connecting circuits in circuits. 2. Under abnormal (overload) conditions, the fuse acts as a safety protection element in the circuit and safely cuts off and protects the circuit by fusing itself. 2. Working principle of current fuse: When the fuse is energized, the heat converted by electrical energy causes the temperature of the fusible body to rise. When the normal operating current or the allowed overload current passes, the heat generated radiates to the surrounding environment through the fusible body and the outer shell, and the heat dissipated through convection, conduction, etc. gradually reaches a balance with the generated heat. If the heat generated is greater than the heat dissipated, the excess heat will gradually accumulate on the fusible body, causing the temperature of the fusible body to rise; when the temperature reaches and exceeds the melting point of the fusible body, the fusible body will melt and fuse. Cutting off the current plays the role of safety protection circuit. 3. Classification of current fuses: 1. According to the appearance size, they are divided into: φ2, φ3, φ4, φ5, φ6 and others. 2. According to the fusing characteristics, it is divided into: fast fusing type, medium delay fusing type, and delayed fusing type. (It can also be divided into express and strong delay). 3. According to the breaking capacity, it is divided into: low breaking type, high breaking type (can also be divided into enhanced breaking type). 4. According to safety standards (or regions of use), they are divided into: UL/cUL (North America) specifications, IEC (China, Europe, etc.) specifications, MIT/KTL (Japan/South Korea) specifications, etc. In many electronic devices, fuses (FUSE) are indispensable. Since Edison invented the first plug-type fuse in the 1890s, which enclosed a thin wire in a desk lamp holder, there have been more and more types of fuses and their applications have become more and more widespread. Here are some fuse parameters, selection and application common sense. The ratings and performance indicators of the fuse are determined based on laboratory conditions and acceptance specifications. There are many authoritative testing and appraisal organizations in the world, such as UL certification of Underwriters Laboratories in the United States, cUL certification of Canadian Standards Association, MTTI certification of Japan’s Ministry of International Trade and Industry, and ICE certification of International Electrotechnical Commission. 1 The selection of fuse involves factors a. Normal operating current. b.Applied voltage applied to the fuse. c. Abnormal current requiring the fuse to be disconnected. d. The minimum and maximum time allowed for abnormal current to exist. e. Ambient temperature of the fuse. f. Pulse, inrush current, surge current, starting current and circuit transient value. g. Are there any special requirements beyond the fuse specifications? h. Dimensional limitations of the installation structure. i. Required certification body. j. Fuse holder:
