OEM 20D 471k Metal Oxide Varistor Capable Of Withstanding High Surge Current Impact

The varistor is the most widely used voltage limiting device. Varistors include silicon carbide varistors and zinc oxide varistors.
Zinc oxide (ZnO) varistor is commonly used, it is mainly based on zinc oxide as raw material, adding a variety of trace metal oxides, mixed molding, sintered and assembled as an overvoltage protection device, its outer package Epoxy resin (pigments can be added).
It is equivalent to a variable resistor, which is connected in parallel in the circuit. When the circuit is in normal use, the impedance of the varistor is very high, and the leakage current is very small, which can be regarded as an open circuit and has almost no effect on the circuit. But when a very high surge voltage comes, the resistance value of the varistor drops instantly (its resistance value can be changed from MΩ (megohm) level to mΩ (milliohm) level), so that it can flow through a large current, while clamping the overvoltage to a certain value. Since the surge withstand capability of a varistor depends on its physical size, it is possible to obtain different surge current values.
Characteristics of varistors
(1) Advantages: the voltage range is very wide, from several volts to several thousand volts, the surge current can be from tens to several thousand amperes, the response speed is fast, there is no polarity, no freewheeling, and the peak current withstand capacity is large. low price.
(2) Disadvantages: The clamping voltage is relatively high, which can generally reach 2 to 3 times the working voltage. In addition, pressure
The leakage current of the varistor increases with the increase of the number of surge impacts. The response time is longer and the parasitic capacitance is larger.
(3) Applicable occasions: DC power lines, low-frequency signal lines, or used in series with gas discharge tubes for AC power lines.

Specifications: