Varistor performance and rules of use

1. The performance of varistor

(1) The varistor is a non-linear resistance element mainly composed of zinc oxide. The surge current tolerance and nonlinear coefficient of the device are very large. When the threshold voltage is lower than the threshold voltage, the resistance is very high, and almost no current flows. The threshold voltage and the resistance are drastically reduced, and the amplified current can be discharged. Due to this characteristic, as a protective element for electronic and electrical equipment, the absorption of abnormal voltage and the absorption of lightning surges play a large role;

(2) The varistor is generally used in parallel in the circuit. When the voltage across the resistor changes abruptly, the short circuit of the resistor blows the current fuse to protect it. Varistors are used in circuits and are often used for power supply overvoltage protection and regulation. Since the varistor has a large parasitic capacitance, it is used in an AC power system, and a considerable leakage current is generated. When the varistor with poor performance is used for a period of time, the leakage current may become hot and burst due to the leakage current. The performance and quality of varistor are closely related.

2. Rules for the use of varistor

(1) Regardless of the change in voltage, its large fluctuation value cannot exceed the large allowable value of the varistor. If the continuous operation voltage exceeds the large allowable value, the use time of the varistor is reduced;

(2) When the varistor is connected between the power line and the ground, the voltage between the power line and the ground may increase due to some reasons such as lack of good grounding. The varistor equipment we use must use ratio a higher voltage between the power line and the earth;

(3) The current absorbed by the varistor during the working process is as small as possible than the flow rate of the product;

(4) When the varistor is used in parallel in the power supply circuit, if the overvoltage across the resistor changes abruptly, the short circuit of the resistor will blow the fuse in the circuit, thereby protecting other electronic components and circuits. If a varistor cannot meet the requirements of overcurrent, a plurality of varistors should be used in parallel. When selecting a shunt varistor, select the resistors with the same parameters for pairing to ensure uniform distribution of overcurrent.