Ceramic gas discharge tube is a kind of surge protector, like other patch discharge tubes, RJ45 type two-in-one surge protector, etc. Most of the working principle is the same, but different models , materials, parameters, then there is a big difference in terms of price and performance will be, so the choice of ceramic gas discharge tube or when the need to understand the relevant knowledge, here's a look ceramic gas discharge tube and the principle of selection bar .
1 Under the rapid pulse impact, the gas ionization of the ceramic gas discharge tube takes a certain time (generally 0.2 to 0.3 μs, and the fastest is also about 0.1 μs), so that a sharp pulse with a higher amplitude leaks to the back. To suppress this sharp pulse, there are several methods: a, parallel capacitor or varistor on the discharge tube; b, series inductance behind the discharge tube or leave a proper length of transmission line to attenuate the sharp pulse to a lower Level; c, using a two-stage protection circuit, with the discharge tube as the first stage, the TVS tube or the semiconductor overvoltage protector as the second stage, and the two stages are isolated by resistors, inductors or self-recovery fuses.
2 DC breakdown voltage Vsdc selection: The minimum value of the DC breakdown voltage Vsdc should be greater than 1.2 times the highest peak voltage or the highest signal voltage that may occur.
3 Selection of impulse discharge current: It should be selected according to the maximum surge current that may occur on the line or the maximum surge current that needs protection. The discharge current of the discharge tube should be calculated according to the nominal impulse discharge current (or half of the single impulse discharge current).
4 ceramic gas discharge tube due to large breakdown voltage error, generally not used in parallel. Â
5 Freewheeling problem: In order to make the discharge tube normally extinguish the arc after the impact breakdown, in the place where there is a possibility of freewheeling (such as in the active circuit), the varistor or self-recovery fuse can be connected in series on the discharge tube. The freewheeling is made smaller than the holding current of the discharge tube. Â
More than said so much, summed up below these points, we ceramic gas discharge tube selection, when you can note the following:
1. DC breakdown voltage value.
2. Determine the highest instantaneous voltage value that the line can withstand
3. Withstand current capability
4. The overcurrent of the discharge tube keeps the voltage as high as possible
5. The gas discharge tube must be equipped with a suitable short circuit device at this time to avoid burning for a long time.
1. DC breakdown voltage value.
2. Determine the highest instantaneous voltage value that the line can withstand
3. Withstand current capability
4. The overcurrent of the discharge tube keeps the voltage as high as possible
5. The gas discharge tube must be equipped with a suitable short circuit device at this time to avoid burning for a long time.
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