Characteristics of PTC thermistor
The PTC effect originates from the nature of the grain boundary and the precipitated phase between the grain boundaries of the ceramic, and changes significantly with the type, concentration, and sintering conditions of impurities. Recently, among thermistors that have been put into practical use are silicon temperature-sensitive elements using silicon chips. This is a high-precision PTC thermistor, which is made of n-type silicon, and the electrons scattered by the impurities in it are scattered as the temperature rises. Increases, and thus the resistance increases.
PTC thermistor appeared in 1950, followed by PTC thermistor with barium titanate as the main material in 1954. PTC thermistors can be used for temperature measurement and control in industry, as well as for temperature detection and adjustment of certain parts of automobiles. They are also widely used in civilian equipment, such as controlling the water temperature of instantaneous boilers, air conditioners and cold storage, Use its own heating for gas analysis and wind speed machine and other aspects. The following is a brief introduction to an example of the application of heating and overheating protection to heaters, motors, transformers, high-power transistors and other electrical appliances.
In addition to being used as a heating element, PTC thermistor can also function as a “switch”. It has three functions: sensitive element, heater and switch, called “thermal switch”, as shown in Figures 2 and 3. Show. The current passing through the element causes the temperature to rise, that is, the temperature of the heating element rises. When the Curie point temperature is exceeded, the resistance increases, thereby limiting the increase in current, so the decrease in current causes the temperature of the element to decrease, and the decrease in resistance value causes the circuit current Increase, the temperature of the component rises and repeats itself, so it has the function of keeping the temperature in a specific range, and it also plays the role of a switch. Using this temperature resistance characteristic to make a heating source, as heating elements, heaters, electric soldering irons, drying wardrobes, air conditioners, etc., can also play a role in overheating protection for electrical appliances.
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