Varistorler

Varistorler is the Turkish plural form of varistor, a type of voltage-dependent resistor used for surge protection. In English-language texts the term varistors is commonly used to refer to the same devices.

A varistor is a non-linear two-terminal component whose resistance decreases as the voltage increases, responding to surges with a sharp rise in conductance. Metal-oxide varistors (MOVs) are the most widespread kind and are typically formed from sintered zinc oxide grains with metal electrodes, packaged as discs and available in radial-lead or surface-mount configurations. They are non-polar, meaning they respond to voltage in either direction.

Operation and ratings: Under normal operating voltage, a varistor presents a high resistance and little current. When a transient exceeds its threshold, the device clamps the voltage by diverting surge current, protecting downstream circuitry. Key specifications include varistor voltage or clamping voltage, energy rating (joules), surge current capability, and tolerance. MOVs can exhibit temperature and rate-of-rise dependent behavior and may age with repeated surges, reducing their clamping effectiveness over time.

Applications: Varistorler are widely used for surge suppression in AC mains power supplies, consumer electronics, telecom and data lines, and automotive systems. They are often placed across line-to-line or line-to-ground paths and, in some designs, paired with fuses or thermal guards to isolate the device after a fault. Variants include radial-lead, surface-mount, and high-energy MOVs, as well as alternative protection devices such as transient voltage suppressor diodes.

Reliability and safety: MOVs can degrade or fail short after severe transients, necessitating periodic testing and timely replacement in critical equipment. They are chosen to provide a margin between normal operation and clamping thresholds while meeting energy and environmental requirements.