Electronic devices rely on stable electricity for normal operation. However, during thunderstorms, voltage surges can occur. Even if lightning doesn’t strike directly, high-voltage pulses can be induced in power or signal lines. These surges are short in duration but high in energy—enough to destroy devices or even cause fires.
To handle such surges, electronic devices use a critical protective component—the varistor.
How Varistors Work
A varistor is voltage-sensitive:
At normal voltage, it has high resistance and does not conduct.
When voltage exceeds its threshold, resistance drops sharply, allowing current to flow to ground or neutral, clamping the voltage and protecting downstream circuits and components.
Common Misconception: Varistors Are Polarity-Free and Can Be Installed Anywhere
While varistors don’t have polarity, installation location matters greatly. Incorrect placement can render the varistor ineffective or even cause accidents.
Varistors should also be used in combination with fuses. Over time, varistors may age, leakage current increases, and the device may overheat or short-circuit.
If a varistor overheats alone, it can bulge, crack, smoke, or ignite.
When paired with a fuse, the fuse melts automatically in case of varistor failure, cutting off current and preventing fire.
Conclusion
For proper circuit protection, varistors must be:
Installed in the correct position.
Paired with a fuse for safety backup.
Correct installation ensures the varistor effectively clamps voltage surges, protects circuits, and keeps electronic devices operating safely.
This article is provided by JYH HSU (JEC) Electronics. JEC is a research, development, production, and sales-oriented company specializing in manufacturing and selling various electronic components such as capacitors and resistors.
Post time: Jan-05-2026