Varistor is a familiar word for technical engineers. So for small projects, it should be a thorough understanding of the time and to explore the function of the varistor and its performance in this area of knowledge. Small series in this is not around the topic, in this? From the technology of small as we bring is: with basic properties of varistor varistor in circuit and protection function. The following is a small series for everyone to prepare the data analysis:
Varistor in circuit function:
The varistor is mainly used in transient overvoltage protection, but it is similar to the volt ampere characteristics of the semiconductor voltage regulator, it also has a variety of circuit components, such as:
(1) high voltage DC current regulator, the stable voltage can be as high as several thousand volts, which is silicon voltage regulator can not be achieved
(2) voltage fluctuation detection element.
(3) DC battery shift element.
(4) equalizing element.
(5) fluorescent start element Basic properties of varistors for protection:
(1) protection characteristics, when the impact of the impact of the source of strong (or shock current Isp=Usp/Zs) does not exceed the specified value, the varistor voltage limit does not allow the object to be protected by the impact withstand voltage (Urp).
(2) shock resistance, that is, the varistor itself should be able to withstand the prescribed impact current, impact energy, as well as the impact of repeated power average power.
(3) there are two life characteristics, one is the continuous working voltage life, that is, the varistor should be able to work reliably in the specified environment temperature and system voltage conditions (hours). The two is the impact of life, that is able to reliably withstand the impact of the number of times.
(4) after the intervention system, in addition to the "safety valve" protection, but also bring some additional effects, which is called the "two effect", it should not reduce the normal performance of the system. The factors to consider when there are three, one is capacitance varistor itself (tens to tens of thousands of PF), the two is the leakage current in the system voltage, three nonlinear current varistor effect on other circuits by coupling the source impedance.