Basic performance of protective varistor

(1) Protection characteristics, when the impact strength of the impact source (or the inrush current Isp=Usp/Zs) does not exceed the specified value, the limiting voltage of the varistor must not exceed the impulse withstand voltage (Urp) that the protected object can withstand. .

(2) Impact resistance, that is, the varistor itself should be able to withstand the specified inrush current, impact energy, and the average power of multiple impacts.

(3) There are two life characteristics, one is the continuous working voltage life, that is, the varistor should be able to work reliably for a specified time (hours) under the specified ambient temperature and system voltage conditions. The second is the impact life, that is, the number of times that the specified impact can be reliably received.

(4) After the varistor is involved in the system, in addition to the protection function of the "safety valve", it will bring some additional effects. This is called the "secondary effect", which should not reduce the normal working performance of the system. There are three main factors to consider at this time. One is the capacitance of the varistor itself (tens to tens of thousands of PF), the other is the leakage current at the system voltage, and the third is the nonlinear current of the varistor through the source impedance. The effect of coupling on other circuits.