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A test of Metal Oxide Varistor for protect the power supply

Date: 2014-12-23 click times: 3239

More senior people in the industry know that in the past, the power of applications. Power lines across the varistor components have appeared on fire case, lead to other components on the circuit near the accident were also burned.

Thus many manufacturers analysis and summarized, varistors on fire phenomenon can basically be divided into two types:
1.Failure after aging, which means that low resistance linearized resistor gradually increased, the leakage current increases and intensively flows into malignant weak point, the weak point of the material melts, forming a short circuit hole of about 1kΩ, power continues to drive a large current sink One the short circuit, the formation of heat and fire. Such incidents usually by one a series of hot-melt pressure-sensitive resistors to avoid contact. Hot melt contact with the resistive element should have a good thermal coupling, when the maximum surge current flows does not disconnect, but is disconnected when the resistor temperature exceeds the upper limit operating temperature. The results show that, if there is a manufacturing defect varistors, prone to early failure, many times less intense electric shock effect, and will accelerate the aging process, so that the failure of aging appear earlier.
2.Transient overvoltage damage, which refers to a strong transient over-voltage resistors perforation, leading to higher current and heat of fire. The whole process occurs in a relatively short period of time, as well as hot melt on contact set resistor fuse too late. In the three-phase power protection, the varistor between N-PE line of fire to burn a higher probability of accidents, mostly belong to this one case. After corresponding countermeasures focused varistor No fire damage.
In response, manufacturers and users jointly carried out extensive research and analysis, but also take the appropriate measures, which greatly reduces the occurrence of such a significant accident (but not eliminate), therefore, the use of safety varistor still is worth paying attention to the need to continue to study and solve the issue.

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