Jännitevkauksiin

Jännitevkauksiin, often translated as voltage-dependent resistors or varistors, are electronic components whose electrical resistance varies with the applied voltage. They are designed to protect electronic circuits from transient voltage spikes, such as those caused by lightning strikes or power surges.

The core principle of a jännitevkauksi is that at normal operating voltages, their resistance is very high, effectively acting as an open circuit and drawing negligible current. However, when the voltage across them exceeds a certain threshold, known as the clamping voltage or varistor voltage, their resistance drops dramatically. This rapid decrease in resistance allows a large current to flow through the jännitevkauksi, diverting the excess energy away from the sensitive components of the circuit and dissipating it as heat. Once the voltage returns to normal levels, the jännitevkauksi's resistance increases again, and it returns to its high-impedance state.

Jännitevkauksiin are commonly made from semiconductor materials, most notably zinc oxide (ZnO) in the case of Metal Oxide Varistors (MOVs). The microstructure of these materials, consisting of semiconductor grains separated by grain boundaries, is crucial to their voltage-dependent behavior. The grain boundaries act as p-n junctions, which are normally reverse-biased and exhibit high resistance. When the voltage is high enough, these junctions break down, leading to a significant reduction in overall resistance.

These components are widely used in power supplies, surge protectors, telecommunications equipment, and automotive electronics to safeguard against overvoltage events and prolong the life of connected devices. Their primary function is to act as a sacrificial element, absorbing the damaging energy of voltage transients.