Application type of SPD varistor

What is the application type of SPD varistor? Let's make a brief analysis. According to the usage, the purpose of applying the varistor should be that the voltage/current acting on the varistor is different. Therefore, the requirements for Barrister are also different, and distinguishing these differences is crucial for correct use. Varistors can be divided into two categories according to the purpose of use. 1. Varistor for protection. 2. Varistor for circuit function

What is the use of SPD varistor

& nbsp; & nbsp; & nbsp; The characteristic of SPD varistor is that when the voltage added above is lower than the threshold value“ UN” The current flowing is very small. Equivalent to closed valve. When the voltage exceeds UN, the resistance will decrease, the flow current will surge, and the impact on other circuits will be greatly reduced, thus reducing the impact of overvoltage on subsequent sensitive circuits. Using this function, the abnormal overvoltage that often occurs in the circuit can be suppressed, thus protecting the circuit from voltage damage

For example, zinc oxide varistor is used in the power circuit of our home color TV, and the voltage used here is 470V. When the transient surge voltage (non effective value) exceeds 470V, the varistor reflects its clamp characteristics. Reducing the excessive voltage will make the rear circuit work within the safe range

How to protect resistance

(1) It must meet the requirements of various technical standards such as voltage reducer for power supply protection, signal line, cable protection, etc

(2) According to the different continuous working voltage applied to the varistor, the varistor used across the power line can be divided into two types: AC or DC, and the aging characteristics of the varistor under these two voltage stresses are different

(3) According to the abnormal overvoltage characteristics that Barrister can withstand, Barrister can be divided into three types: surge suppression type, high power type and high energy type
Surge suppression type: refers to the pressure reducer used to suppress transient overvoltage (such as lightning overvoltage and switching overvoltage). The occurrence of this temporary overvoltage is random and non-periodic, and the peak value of current and voltage may be large. Most pressure resistors fall into this category

High-power type: refers to the pressure resistor (for example, the pressure resistor connected to the switching power converter) used for the continuous pulse group with absorption cycle. It can be seen from this that the impulse voltage period occurs, and the energy value can be calculated generally. The voltage peak is small, but the frequency is high, so the average power is quite large

High-energy type: refers to the voltage reducer that absorbs the magnetic energy of large induction coils such as generator magnetic coil and crane electromagnet coil. The main technical index of these applications is energy absorption capacity

The protection function of theSPD varistormay be repeated many times in most applications, but sometimes it will become a current fuse and so on“ One time” Protector. For example, a short-circuit contact voltage reducing resistor connected to some current transformer loads