How to use varistors correctly? According to the different use of the scene, the application of varistor purposes, the role of the varistor voltage / current stress is not the same, so the requirement...
How to use varistors correctly? According to the different use of the scene, the application of varistor purposes, the role of the varistor voltage / current stress is not the same, so the requirements of the varistor is not the same, pay attention to distinguish this difference.
According to the purpose of the use of different, varistor is divided into: circuit function with varistor and protective varistor.
A, circuit function with varistor
Varistor is mainly used in transient overvoltage protection, but it is similar to the semiconductor regulator tube volt-ampere characteristics, but also it has a variety of circuit components function, the role of:
(1) DC high voltage small current regulator components, the stable voltage can be as high as several thousand volts or more, which is silicon regulator can not be achieved.
(2) voltage fluctuation detection element.
(3) DC battery shift components.
(4) pressure equalizer.
(5) Fluorescence start element.
B, protective varistor
(1) to distinguish between power protection, or signal lines, data line protection with varistors, they have to meet the requirements of different technical standards.
(2) Depending on the continuous operating voltage applied to the varistor, the varistor for the power supply line can be divided into two types: AC or DC, and the varistor under these two kinds of voltage stresses Aging performance is different.
(3) According to the varistor bear the abnormal over-voltage characteristics of different varistors can be divided into surge suppression, high power and high energy type of these three types.
Surge suppression type: refers to the suppression of lightning overvoltage and over-voltage and other transient overvoltage varistor, the occurrence of transient overvoltage is random, non-periodic, the peak current and current may be Big. Most varistors all fall into this category.
High power type: refers to the varistor for the continuous cycle of the group of varistors, such as connected to the switching power supply varistor, where the impact voltage cycle occurs, and the cycle we can see that the energy value can generally be calculated Out, the peak voltage is not large, but because of the high frequency, the average power is quite large.
High energy type: refers to the absorption of the generator excitation coil, lifting solenoid coil and other large inductor coil in the magnetic energy of the voltage transformer, for such applications, the main technical indicators of energy absorption capacity.
Varistor protection, the vast majority of applications, it can be repeated many times, but sometimes it will be made of current fuse as a "one-time" protection device. Such as a short-circuit contact varistor connected to some current transformer loads.