8) V-I properties of gas discharge tubes


The Micro-Gap surge absorber is a type of discharge tube. The discharge in the tube changes
from pre-discharge to glow discharge, then to arc discharge as illustrated in Fig.9.
The illustration below also shows the V-I characteristics between voltage and current for the discharge tube.
When the tube is discharging, electric current flows and moves to glow discharge, then to arc discharge as the discharge voltage decreases. Conversely, when the discharge decreases, the voltage increases as it moves from arc discharge to glow discharge.

 

 

 

 

● Pre-glow discharge
The voltage to maintain the discharge is equivalent to the DC sparkover voltage. A faint light can be seen in the tube.
● Glow discharge
The constant voltage rate remains as the current changes. The voltage to maintain the discharge depends on the electrode material and the gas in the tube. The discharged light covers a portion of the electrodes.
● Arc discharge
At the end of discharge a large current flows through the part and it emits a bright light. This is the maintaining voltage

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