Home appliances, also known as household appliances, refer to appliances that use electrical energy to drive (or mechanize) household chores, such as cooking, food preservation, or cleaning. In addition to the home environment, they can also be used in company or industrial environments. Basically, household appliances are divided into large appliances (white appliances, black appliances) and small appliances. With the development of the electronic information industry and the popularization of household appliances, starting from the localization of color televisions in the 1980s, the development of refrigerators, washing machines, cassette recorders, black and white televisions, household air conditioners, telephones, energy-saving lights, VCDs, DVDs, computers, and programmable switches has improved the quality of life for every Chinese family. The demand for the electronic industry is also increasing, in order to meet the needs of the development of household appliances in terms of quantity, quality, and service. Electronic components have also developed rapidly in this daily household industry, including fuses, self-healing fuses, disposable fuses, plug-in fuses, SMD fuses, SMD capacitors, high-voltage SMD capacitors, SMD resistors, SMD inductors, tantalum capacitors, precision resistors, SMD aluminum electrolytic capacitors, voltage regulator diodes, rectifier diodes, light-emitting diodes, and other electronic components.
A self restoring fuse, also known as a self resetting fuse, is a fuse that, after being blown, can automatically resume use after troubleshooting.
The PPTC self recovery fuse is used in series in a circuit. When the current increases rapidly, the PPTC self recovery fuse changes from a low resistance state to a high resistance state to protect the circuit, and this process is called "action". The resistance of the PPTC fuse in normal working condition is far from that of other components in the Xiao Yuyu resistor. However, in the case of overcurrent, the resistance of the component will increase (act), thereby reducing the current in the circuit to protect other components. This process involves I ² The R principle generates heat inside the heating element, causing a rapid increase in the temperature of the element.
The operation principle of PPTC fuse is a balance of energy. During normal use, the heat generated by the component itself and dissipated into the environment will form a balance at relatively low temperatures.
When the external temperature remains relatively balanced, the current flowing through the PPTC fuse increases, and the temperature of the fuse also increases. When the current or ambient temperature continues to increase, the PPTC fuse element will reach a higher temperature. If the temperature increases at this point, the generated heat energy will be greater than the dissipated heat energy. Yes, the temperature of the PPTC fuse element continues to increase, At this stage, a small temperature change will cause a significant increase in resistance, which is the conventional action process area of PPTC components. The significant change in resistance leads to a corresponding decrease in the current in the circuit. This relationship will continue until the component resistance reaches a higher value on the curve. As long as voltage stability is provided, the component will remain in working condition. Once the voltage decreases to a certain value or the power supply is disconnected, the component will be restored and can continue to be used.
It can be seen that the operating current and operating current of PPTC components vary with temperature. Each available component can be divided into three partial areas. Zone A is the PPTC fuse element action state (high resistance value) area. Zone B is the area where PPTC components maintain normal circuit operation. Zone C is in the area of possible or no action (depending on the resistance of the component).
Current action time curve: The current action time characteristic curve of PPTC components in static air at 0 ℃ and 75 ℃. These two curves are different because the thermal energy of the original action comes from I ² R heat or external environmental temperature. At 75 ℃, the temperature from the outside is much higher than at 0 ℃, so the additional I required for self recovery fuse action ² The relative reduction of R heat leads to a relatively small action current within the same action time (or a decrease in action time under the same action current).
The figure shows the relationship curve between the recovery time and resistance after the PPTC fuse is activated. In the figure, we can see that even after a few hours, the component resistance is still greater than the initial resistance, and the reduction process of resistance will continue for a long time before the resistance finally approaches the initial value.
However, this time can be a few days or several years, but it is possible to restore the PPTC self recovery fuse to its initial value after operation. So when choosing a PPTC recoverable fuse, it is necessary to consider the value of R1max when determining the holding current, which is the maximum resistance value after 1 hour of action recovery.
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