Varistor five overheating protection technology Knowledge of electrical resistance

by:Thermistor-Mov     2020-06-22
Varistor five overheating protection technology varistor is mainly introduced in this paper five kinds of overheating protection technical analysis, this article about 1000 words, read the full text to 10 minutes. ( 1) Thermal fuse technology. Waxes for this technology is to protect the low melting point metal through a certain process in a pressure sensitive resistance, the varistor leakage flow is big, the temperature rise to a certain extent, low melting point metal fusing, thereby the varistor removal from the circuit, can effectively prevent the varistor burst into flames. But hot melt fuse reliability problems, and to strengthen environment of the thermal cycle Rio only reliable life for five years. In the environment of the thermal cycle, thermal fuse need to be replaced periodically in order to maintain normal operation. ( 2) Using the spring pulls low melting point solder technology. This technology is currently the vast majority of the lightning protection device type pressure limiting and the adopted technology of the SPD in the varistor pins add a low melting point solder welding points, and then use a spring will pull the welding points, the varistor leakage flow is big, the temperature rise to a certain extent, welding solder fusing point, under the action of tension of the spring weld rapid separation, thus the varistor from circuits of resection, linkage alarm contacts at the same time, an alarm signal. Because of the low melting point metal will flow and cracks in the stress point, low melting point solder in the spring tension contact solder will also flow and cracks, so the problem of the device solder is aging, which leads to device would disconnect a cause. ( 3) Temperature fuse technology. The technology will fuse in series with the pressure sensitive resistance and temperature, the heat conduction is used to change the leakage current on the pressure sensitive resistance heat conduction temperature fuse, temperature rise to set temperature of the temperature fuse, temperature fuse fusing, the pressure sensitive resistance is removed from the circuit. Temperature fuse, in addition to have the same life and reliability problems, using the temperature fuse varistor for overheating protection still exist the following problems: heat conduction path is long, the response speed is too slow, heat is through a heat conduction medium ( Filler material) Shell, temperature fuse, temperature fuse inside filling material, and then spread to the melt temperature of the insurance, thus determines the temperature fuse teaching slow response speed. ( 4) Isolation technique. The technology will varistor is installed in a sealed box body, and other circuits are isolated, prevent the varistor the spread of smoke and flame. In the case of failure of all sorts of backup protection, isolation technique is a simple and effective method, but need to take up a big space for equipment, but also to prevent the smoke and flame out from the box body opening lead. ( 5) Sealing technology. To prevent varistor in failure when smoke, fire and crack, some vendors will adopt the technology varistor potting up, but as a result of varistor will appear within fails to pull arc, lead to seal material failure, and generate carbon, carbon produce and can make the arc is maintained, so often lead to internal short circuit and blackened equipment, serious and even cause the entire equipment room blackened. Experiment shows that pressure sensitive resistance of heat shrinkable casing, due to the pressure sensitive resistance of heat dissipation is affected, the power dissipation is reduced, thus affecting the power frequency voltage tolerance capacity of varistor, from another perspective, the heat affected will also accelerate the aging of varistor, affect the service life of the varistor. 文章/ ymdzwzgrbh。 HTML this paper label: an article on resistance pressure sensitive resistance: varistor symbols, pressure sensitive resistance under the action of an essay: what are SMD resistor value judgment method
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