Oct. 13, 2023
A varistor is a special type of voltage-limiting protective component with nonlinear voltage-current characteristics. It is highly voltage-sensitive, and its resistance changes with variations in voltage within a specified range. Its primary function is to absorb excess current and protect circuits from voltage spikes.
When the voltage is low, the varistor has a high resistance, allowing only a minimal current to pass through, effectively acting like a closed valve. However, when the voltage exceeds a certain threshold, the resistance of the varistor dramatically decreases, allowing a surge of current to flow through, similar to an open valve. This property enables it to absorb excess current.
Varistors protect circuits and devices primarily through the following mechanisms:
Charge Neutralization: When the voltage exceeds a certain level, the resistance of the varistor drops sharply, leading to a rapid increase in the current flow. During this process, the current flow is transient, causing the rapid neutralization of charges. This prevents continuous overvoltage from harming the circuit and electronic components.
Heat Dissipation: When current passes through the varistor, it generates heat. Some of this heat is absorbed by the varistor itself and converted into thermal energy, while the rest is dissipated through thermal conduction and radiation into the surrounding environment. This cooling effect helps maintain the normal operating temperature of the circuit and prevents thermal breakdown caused by overvoltage, effectively safeguarding the circuit and electronic components.
In addition to its role in absorbing excess current, varistors are favored for their simple structure, compact size, and lightweight characteristics, making them an indispensable part of many electronic devices.
This article is provided by JYH HSU Electronics, a manufacturer of electronic components such as capacitors and resistors.
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