There are so many types of circuit protection components, and it can be hard to tell them apart... This article will help!

Latest update time：2021-09-03 22:26

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Keywords : circuit protection, GDT, fuse, circuit breaker, varistor, component

Circuit protection is fundamental to circuit design. It involves a wide variety of components, and it's crucial to be familiar with and understand the characteristics of each. This article will introduce and compare common circuit protection components .

Gas Discharge Tube (GDT) —This is a voltage-driven component. A GDT remains in the open circuit until the voltage in the circuit reaches a certain level. When the voltage reaches a certain level, the gas in the GDT ionizes and conducts electricity, connecting the high-voltage level to ground. Once the high voltage decreases, the gas deionizes, and the GDT returns to the open circuit state until the next surge. Compared to other circuit protection components, GDTs can absorb significantly more transient energy.

Two-pole GDT - used for line-to-line or line-to-ground circuits.

Three-pole GDT - can be used for a portion of a line-to-line or line-to-ground circuit simultaneously.

Fuse - A fuse consists of a metal strip or fusible element installed between two electrical terminals. When current flows through the metal strip, it heats up. When it heats enough, it melts and breaks, breaking the circuit. At this point, the damaged fuse needs to be replaced to restore the circuit. Fuses are the cheapest circuit protection device and are generally the easiest to use.

Circuit Breaker - Similar to a fuse, a circuit breaker protects an electrical circuit from excessive current, but a circuit breaker does not destroy itself when it opens the circuit and can be reset.

Varistors —These are voltage-driven components. When no voltage is applied, a varistor typically exhibits high resistance. As voltage levels increase, its resistance decreases. When high voltage passes through a varistor and exceeds its breakdown voltage, the component rapidly reduces its resistance and clamps the voltage to a safe level. At this point, the resistor partially conducts current and absorbs excess energy to protect the circuit. Once the voltage drops, if the component is intact, it returns to a high resistance state and can be used normally.