Ring varistor

Ring varistor is a resistor that varies with voltage over a range of current and voltage, perhaps a resistor that is sensitive to voltage. The English name is “Voltage-dependent resistor” and is abbreviated as “VDR”, perhaps called “Varistor”. The resistor body data of the ring varistor is a semiconductor, so it is a type of semiconductor resistor. Many of the “zinc oxide” (ZnO) ring-shaped varistors used today are composed of a divalent element (Zn) and a hexavalent element (O). Therefore, from the point of view of the data, the zinc oxide ring varistor is an “II-VI group oxide semiconductor”.
The ring varistors, abbreviated as VSR, is a voltage-sensitive nonlinear overvoltage maintenance semiconductor component. It is indicated by the text symbol “RV” or “R” at the top of the circuit.

ring varistor

Ring varistor action:

The biggest characteristic of a ring varistor is that when the voltage applied to it is lower than its threshold, the current flowing through it is extremely small, equivalent to a valve that is closed, and when the voltage exceeds UN, it flows through it. The current surges, which is equivalent to the valve opening. Using this function, the circuit can be protected from overvoltage by pressing the abnormal overvoltage that often occurs in the circuit. Generally, a ring-shaped varistor is high-resistance at a low voltage and becomes a low-resistance state after exceeding a certain voltage. It is primarily used for overvoltage maintenance and for absorbing surge currents. For example, in the overvoltage leakage maintenance switch, a ring-shaped varistor is used as a sensitive component.
One parameter on ring varistors are the voltage parameter. The ring varistor is connected in parallel with the electric appliance. If the voltage exceeds its value, the ring varistor is turned on, and the voltage is lowered to maintain the electric appliance. When the voltage at the two ends of the ring-shaped varistor is greater than the resistance of the ring-shaped varistor, the ring-shaped varistor is turned on, the line current becomes large, the fuse is burned, and then the maintenance appliance is not damaged by the high voltage.