Detailed reference parameters of varistor
Pressure sensitive voltage Voltage Varistor:
As the name suggests, it is the threshold voltage (i.e., the breakdown voltage or the threshold voltage) that is triggered by the pressure sensitive. This is generally a wide range. 220V, for example, is popular to say that when the voltage reaches 220V, the pressure sensitive resistance will be quickly changed from the original state of the circuit breaker, to play a protective role.
Maximum continuous operating voltage Allowable Voltage Max:
This voltage is lower than the voltage of a certain range, to ensure that the work has a high impedance representation of the work voltage. Generally lower than the lower limit of the pressure sensitive voltage to a certain value. With 20K821 for example, the popular saying is the flow, the first open flow can reach 7500A, second times can reach 6500A.
The maximum peak voltage Clamping Voltage Max just as the name suggests, beyond this range of voltage is beyond the reasonable scope of the device, the device will face the risk of damage, the voltage is reduced and may not be restored. Popular to say that in the range of accuracy, the maximum can reach the voltage value. For example 270V error 10% the maximum voltage is 297V.
Maximum energy (energy tolerance)
The energy absorbed by the pressure sensitive resistor is generally calculated by pressing W=kIVT (J)
Where I - the peak of the flow through the pressure sensitive resistance;
V - voltage at both ends of the pressure sensitive resistor when the current I flows through a voltage - sensitive resistor;
T - current duration;
K - current I waveform factor.
Square wave 2ms of k=1,
8/20 S wave k=1.4,
10/1000 mu k=1.4 s.
The resistance of the 2ms square wave, the absorption of energy up to 330J per square centimeter; on the 8/20 S wave, the current density of up to 2000A per cubic centimeter, which shows that his flow capacity and energy tolerance are very large.
In general the varistor chip size is bigger, its energy tolerance is large, high impact current is larger, the varistor shall also be considered often less energy and over voltage but the frequencies of the high number, such as tens of seconds, one or two minutes once or several times over voltage, then they should consider the average power of varistor can absorb.