陶瓷氣體放電管
陶瓷氣體放電管 is the most widely used switching device in lightning protection equipment. Gas discharge tube (GDT) uses metallized ceramic tubes and two or more electrodes to seal one or more discharge gaps. Inert gas is filled inside the ceramic gas discharge tube, and active electron powder is coated on the effective electron emission surface of the electrodes. The distance between electrodes less than 1mm can ensure the stability of the breakdown voltage of the discharge tube. The ceramic gas discharge tube is cylindrical in shape and has two structural forms with and without leads. 陶瓷氣體放電管s are used in communication or signal circuits with AC not exceeding 1200V and DC not exceeding 1500V, especially in the protection of information and signal systems. The tube is filled with an inert gas with stable electrical properties, such as argon and neon.
下圖給出了不同條件下氣體放電管的電路符號。
當氣體放電管兩端的電壓達到其直流放電電壓時，內部氣體會擊穿並放電。氣體放電管的伏安特性是非線性的，擊穿過程分為三個階段：擊穿前直流電阻保持在10°Ω以上；擊穿瞬間阻抗和管壓降急劇下降，導通電流劇烈上升；擊穿後阻抗和管壓降立即保持在很低的水平，並持續到線上電壓低於氣體放電管的電弧電壓，然後自行回到開路狀態。
氣體放電管電路符號
