What is a Varistor?
A Varistor is an electronic component that is commonly used to protect circuits from voltage spikes and surges. It is also known as a Voltage Dependent Resistor (VDR), and it is made up of semiconductor materials, such as zinc oxide, that have a non-linear resistance. The resistance of a Varistor changes with the applied voltage, making it an effective device for limiting transient voltages in a circuit.
Varistors are available in various shapes and sizes, and they are often used in applications where a sudden increase in voltage can cause damage to sensitive electronic components. They are commonly found in power supplies, surge suppressors, and electronic devices that are exposed to transient voltages, such as televisions, computers, and home appliances.
How does a Varistor work?
Varistors work by changing their resistance in response to changes in voltage. When the voltage across the Varistor is below a certain threshold, its resistance is very high, and it does not conduct any current. However, when the voltage exceeds the threshold, the resistance of the Varistor drops rapidly, allowing it to conduct current and limit any further increase in voltage.
This behavior of Varistors is determined by its material properties, such as the thickness and density of the zinc oxide layer, which can be adjusted to suit the specific voltage and current requirements of a particular application. Varistors are designed to tolerate a wide range of voltages, from a few volts to several thousand volts, and they can handle high surge currents for short durations.
Applications of Varistors
Varistors are widely used in electronic circuits for protecting sensitive components from voltage spikes and surges. They are also used in power supplies, motor control systems, and lighting systems, where they provide protection against overvoltage conditions. Varistors are also used in surge suppressors and surge arrestors, which are used to protect electrical equipment from lightning strikes and other transient voltages.
In addition, Varistors are used in communication systems, such as telephone networks and data communication networks, where they provide protection against electromagnetic interference and other noise sources. They are also used in automotive systems, where they protect sensitive electronics from voltage spikes and surges that can occur during starting and charging operations.
Example of Varistor in Circuit Design
One example of a Varistor in circuit design is the surge protector. A surge protector is a device that is used to protect electrical equipment from voltage spikes and surges, which can cause damage or malfunction. A surge protector typically consists of a Varistor and a fuse, which work together to absorb the excess energy and limit the current flow.
In a typical surge protector circuit, the Varistor is connected in parallel with the equipment being protected, and it is designed to conduct current only when the voltage exceeds a certain threshold. When the voltage exceeds the threshold, the Varistor conducts current and absorbs the excess energy, limiting the voltage to a safe level.
Overall, Varistors are an essential component in many electronic circuits, providing protection against transient voltages and ensuring the reliable operation of electronic equipment. Their versatility and effectiveness make them a popular choice for a wide range of applications, from consumer electronics to industrial systems.
