GDTs are packaged in ceramics hermetically with inert gases inside and two (or more) electrodes inserted into it. According to the number of electrodes: There are two types of two-pole discharge tubes and three-pole discharge tubes.

The basic principle of GDT is Gas discharge. At normal operating voltages below the GDT rated DC sparkover voltage, the GDT remains in a high impedance off-state condition. Once the surge overvoltage reaches the pulse breakdown voltage value of the GDT, the electric field strength between the two poles of the GDT will exceed the breakdown strength of the gas, causing the gap discharge to ionize the gas in the tube, and the GDT will on state. At this time, the overcurrent generated by the surge will be discharged to the ground through the GDT, so that the components of the subsequent circuit will not be damaged by the surge. When the surge event subsides and the system voltage returns to normal levels, the GDT will reset into its

high impedance (off) state.  GDTs are often used in the first or first two stages of multi-level protection circuits to discharge lightning transient overcurrent and limit overvoltage. The following introduces the application of Gas Discharge Tubes (GDTs) designed by our SOCAY FAE engineers : Power Solution for AC220V power.

Background：

1. Global warming, more thunderstorms

2. After the power supply is damaged by lightning, it is very harmful

3. After the power supply is damaged by lightning, the maintenance cost is high

4. High surge protective equipment becomes an industry trend

SOCAY Solution and Components：

Gas Discharge Tubes(GDTs)

GDT【SC2E5-600LL】DC Spark-over Voltage：600±20%V，Nominal Impulse Discharge Current（8/20μS）：5kA，Maximum Capacitance＜1.0pF，Minimum Insulation Resistance＞1GΩ；Intermediate protection

GDT【SC2E8-600ML】DC Spark-over Voltage：600±20%V，Nominal Impulse Discharge Current（8/20μS）：10kA，Maximum Capacitance＜1.5pF，Minimum Insulation Resistance＞1GΩ；Advanced Protection

GDT【SC2H8-3500LL】DC Spark-over Voltage：350±20%V，Nominal Impulse Discharge Current（8/20μS）：5kA，Maximum Capacitance＜1.5pF，Minimum Insulation Resistance＞1GΩ；

Varistor(MOV)

MOV1/MOV2/MOV3【14D561K】Varistor Voltage（at1mA）：504V-616V，Withstanding Surge Current（8/20μS）：4500A，Maximum Clamping Voltage（at5A）：925V; Intermediate protection

MOV1/MOV2/MOV3【20D561K】Varistor Voltage（at1mA）：504V-616V，Withstanding Surge Current（8/20μS）：6500A，Maximum Clamping Voltage（at5A）：925V; Advanced Protection

Application：

1.LED street light power supply

2.Switch power supply

3.Air-conditioning power supply

4.Inverter power supply

5.Computer power supply

6.Induction cooker/rice cooker

7.Other AC94V-AC264V power supply

Solution Notes：

1. The solution meets surge test standards such as IEC61000-4-5, GBT17626.5, etc.

2. In the differential mode, MOV with fast response time was used to reduce the surge voltage between L and N lines.

3. In the common mode protection, MOV and GDT are connected in series to the PCB ground or the equipment shell to prevent the leakage current of the MOV.

4. The solution can pass 1.2/50-8/20μS combined wave differential mode, common mode 6.0KV surge test.

Remark: When AC1500V is required in the insulation class voltage test, we recommend GDTs with DC3500V.

To learn more about the application and part number of GDTs, please directly enter the website of Socay  to consult online customer service http://www.socay.com/