Deterioration of the electrically insulating material, such as the arc resistance between the electrodes, can cause the electrically insulating material to catch melamine cyanurate fire and be partially or completely destroyed. The corrosiveness of the combustion products will damage adjacent components, which may cause greater damage. The smoke corrosion caused by this can be evaluated according to the test method invented by the French National (Long Distance) Communication Research Center (CNET). Its test method: In a closed room where the copper wire is exposed to the combustion products of an insulating material, the change in the resistance of the copper wire is measured when the indoor temperature containing saturated water vapor reaches the dew point. When the percentage of resistance increases, apply the following equation to get the CNET value:
In the equation
Ff——Resistance after steel wire test, Ω
Fi——Copper wire initial resistance, Ω
CNETs of less than 20% are considered optimal. In the end the copper wire was completely corroded, broken and broken. Table 4-20 lists some CNET values.Table 4-20 shows the CLF value measured at 55 ° C, 240V (DC) voltage and 95% relative humidity for 14 days. The higher the CLF value, the more severe the corrosion.
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