Varistor is one of the most widely used electronic components at present. In the application process, the aging problem of varistor is the biggest shortcoming, which seriously interferes with the normal and safe operation of the system. So, what method can effectively restrain the aging of varistor? In this paper, two methods are introduced to effectively solve the aging of varistor.
Solution of varistor aging
(1) the varistor is connected in parallel with the ceramic discharge tube, which can solve the problem of performance degradation of the varistor after continuous high current and delay the aging speed. By operating in parallel with the ceramic discharge tube, the varistor starts to work before the discharge tube is turned on, clamping transient overvoltage and releasing large current. After the discharge tube passes, it is shunted in parallel with the varistor to reduce the flow pressure of the varistor. Therefore, the time for the varistor to pass through a large current is shortened, which is helpful to alleviate the degradation of the varistor performance.
During this parallel operation, one problem that engineers should pay attention to is that if the reference voltage Uima of varistor is chosen too low, the discharge tube may not discharge during temporary overvoltage. All the energy of overvoltage is released by varistor, which is not conducive to the value of varistor Uima must be greater than the DC discharge voltage of discharge tube. It must be pointed out that this well-connected combined circuit does not solve the possible freewheeling problem of the discharge tube, so it is not suitable for the protection of AC power supply system.
(2) The varistor is connected in series with the ceramic discharge tube, and the circuit diagram of the series is shown in the following figure
In normal operation, varistor often has a large parasitic capacitor in the circuit system. When applied to the protection of AC power supply system, it will produce considerable leakage current in normal operation. For example, a varistor with a parasitic capacitor of 2nF is set in an AC power supply system of 220V and 50hz, and its leakage current reaches 0.14mA Large leakage current often affects the normal operation of the system. However, when we connect the varistor in series with the ceramic gas discharge tube, the total capacitance of the whole series branch can be reduced to a few because the parasitic capacitance of the discharge tube is very small. In this series combination branch, the discharge tube acts as a switch. If there is no transient overvoltage, the varistor can be isolated from the system, so that the varistor has almost no leakage current. In this way, the reference voltage Uima of the varistor can be reduced without considering the increase of leakage current, so that the performance degradation of the varistor can be slowed down more effectively.
The above content mainly introduces the effective solutions of varistor aging. If you need varistor related products, please leave a message or call: 0755-28100016; Massive varistors are in stock with complete specifications. Welcome to inquire about the price or take samples for testing.
Shenzhen Shunhai Technology Co., Ltd. is an integrated supplier of electronic components, semiconductor devices and protection devices, Mainly engaged in TVS transient suppression diode, ESD electrostatic protector, GDT ceramic gas discharge tube, TSS semiconductor discharge tube, NTC thermistor, varistor, fuse, alloy resistor, chip resistor, precision resistor, wafer resistor, chip fuse, self-recovery fuse, chip capacitor, tantalum capacitor, electrolytic capacitor, aluminum electrolytic capacitor, supercapacitor, connector and other related product lines. Brands can be elected from Huade, Shuokai, Saruiwei, Yineng, Tesscara, KEMET, Tianer, Wangquan, Dayi, Murata, Taiyi, TDK, AVX, Weishi, Fenghua, Huaxin Branch, Sanying, Guoju, Lilong, Housheng, Guangluo, Shunluo, etc.
