Varistor is the most common metal oxide varistor (MOV Metal, Oxide Varistor), it contains a ceramic block composed of Zinc Oxide particles and small amounts of other metal oxides or polymer interval, sandwiched between two metal sheets. The particles at the junction with the adjacent oxide will form a diode effect, due to a large number of random particles, making it equivalent to a lot of back to the low voltage diode is connected, only a very small reverse leakage current, when high voltage, diode due to hot electrons and tunnel effect and reverse circulation collapse, large current. Therefore, the current voltage characteristic curve of varistors has a high degree of nonlinearity: low voltage, high resistance and low resistance at high voltage. What‘s the use of varistors?
The biggest characteristic of the varistors with them when the voltage is lower than the threshold it "UN", the minimum current flowing through it, the equivalent of a closed valve, when the voltage exceeds UN, its resistance value is reduced, so that the current flowing through it in the impact on other circuit changes not to reduce the impact on subsequent small voltage sensitive circuit. By using this function, the abnormal overvoltage in the circuit can be suppressed, and the circuit can be protected from over-voltage damage.
For example: a power supply circuit of our home TV in Zinc Oxide on the use of varistor varistor varistor voltage, here used to 470V, when the maximum transient voltage surge (non effective value) more than 470V, the varistor is the embodiment of his clamping performance, the high voltage low, make the circuit work in a safe range.
As the main component or different brands of metal oxide varistor can sometimes see the name: ZNR (Zinc-Oxide Non-linear Resistor, Zinc Oxide ZOV, nonlinear resistor) (Zinc-oxide Varistor), CNR (Composite Nonlinear Resistor[2]), TNR (Titanium-oxide based Non-linear Resistor, titanium oxide nonlinear resistance, but may also be Toshiba Non-linear Resistor, from Shenzhen the company‘s TG varistor.