What is the purpose of a varistor in an electrical circuit?
1 Answer
The purpose of a varistor in an electrical circuit is to protect sensitive electronic components and devices from voltage spikes or transient overvoltages. A varistor, also known as a voltage-dependent resistor or VDR, is a type of semiconductor device that exhibits a nonlinear resistance characteristic with respect to voltage.
When the voltage across a varistor is below a certain threshold (typically its rated voltage), it acts as an insulator and has a very high resistance, allowing only a small current to pass through. However, when the voltage exceeds its threshold, the varistor's resistance drops significantly, allowing a large amount of current to flow through it. This behavior is in contrast to linear resistors, which maintain a constant resistance regardless of the applied voltage.
During normal operation, a varistor remains in its high-resistance state, which doesn't affect the circuit's performance. However, if there is a sudden surge or spike in voltage, such as from lightning strikes, power surges, or other transient events, the varistor responds rapidly by transitioning to its low-resistance state. This effectively diverts excess current away from sensitive components, preventing them from being damaged by the voltage surge.
Varistors are commonly used as protective components in various electrical and electronic circuits, such as power supplies, surge protectors, motor control circuits, and telecommunications equipment. They provide a cost-effective way to safeguard devices and prevent damage caused by voltage fluctuations or transients that might otherwise result in costly repairs or replacements.
When the voltage across a varistor is below a certain threshold (typically its rated voltage), it acts as an insulator and has a very high resistance, allowing only a small current to pass through. However, when the voltage exceeds its threshold, the varistor's resistance drops significantly, allowing a large amount of current to flow through it. This behavior is in contrast to linear resistors, which maintain a constant resistance regardless of the applied voltage.
During normal operation, a varistor remains in its high-resistance state, which doesn't affect the circuit's performance. However, if there is a sudden surge or spike in voltage, such as from lightning strikes, power surges, or other transient events, the varistor responds rapidly by transitioning to its low-resistance state. This effectively diverts excess current away from sensitive components, preventing them from being damaged by the voltage surge.
Varistors are commonly used as protective components in various electrical and electronic circuits, such as power supplies, surge protectors, motor control circuits, and telecommunications equipment. They provide a cost-effective way to safeguard devices and prevent damage caused by voltage fluctuations or transients that might otherwise result in costly repairs or replacements.