What are the characteristics and applications of varistors (MOV, VDR)?
1 Answer
Varistors, also known as MOV (Metal Oxide Varistor) or VDR (Voltage Dependent Resistor), are electronic components that exhibit nonlinear resistance with changes in voltage. They are primarily used for surge protection in electronic circuits and devices. Let's explore their characteristics and applications:
Characteristics of Varistors:
Nonlinear Resistance: Varistors have a nonlinear voltage-current characteristic. Under normal operating conditions, they exhibit very high resistance, but as the voltage across them increases, their resistance rapidly decreases. This behavior makes them effective in clamping excessive voltage spikes and surges.
Metal Oxide Construction: Most varistors are made of zinc oxide (ZnO) with small amounts of other metal oxides. The grains in the material have different electrical properties, contributing to the nonlinear behavior.
Fast Response Time: Varistors respond very quickly to voltage spikes and surges, providing prompt protection to sensitive electronic components.
Voltage Ratings: Varistors are available in a wide range of voltage ratings, allowing them to be used for various applications with different voltage levels.
Current Rating: Varistors can handle a certain amount of current, which is specified as the maximum peak current they can withstand without damage.
Operating Temperature Range: They have a specified operating temperature range within which they function optimally and offer effective protection.
Leakage Current: Varistors have a small amount of leakage current when subjected to lower voltage levels, but this is generally negligible.
Applications of Varistors:
Surge Protection: The primary application of varistors is in surge protection circuits. They are used to protect electronic devices from voltage spikes caused by lightning strikes, power surges, or electromagnetic interference. Varistors quickly divert excess voltage away from sensitive components, preventing damage.
Voltage Regulation: Varistors can be employed in voltage regulation circuits to maintain a relatively stable voltage level by shunting excess voltage when it exceeds a certain threshold.
Transient Voltage Suppression (TVS): Varistors are widely used as TVS devices in communication systems, power supplies, and data lines to suppress transient voltages and protect sensitive electronic components from damage.
Overvoltage Protection: Various electrical and electronic systems use varistors for overvoltage protection. They safeguard equipment from voltage levels beyond their rated capacity.
Lightning Arresters: Varistors are integral components of lightning arresters installed in electrical power distribution systems and telecommunication networks to protect against lightning-induced surges.
Power Surge Protectors: In surge protectors and power strips, varistors are used to safeguard connected devices from voltage spikes that may occur due to utility grid fluctuations or lightning strikes.
Electronic Circuits: Varistors can be used in various electronic circuits to provide voltage-dependent resistance and filtering applications.
It's important to note that while varistors are effective in handling voltage surges, they are not designed for continuous overvoltage conditions. If subjected to sustained high voltages, they may degrade or fail, so it's essential to use them within their specified limits and in conjunction with other protective measures for comprehensive surge protection.
Characteristics of Varistors:
Nonlinear Resistance: Varistors have a nonlinear voltage-current characteristic. Under normal operating conditions, they exhibit very high resistance, but as the voltage across them increases, their resistance rapidly decreases. This behavior makes them effective in clamping excessive voltage spikes and surges.
Metal Oxide Construction: Most varistors are made of zinc oxide (ZnO) with small amounts of other metal oxides. The grains in the material have different electrical properties, contributing to the nonlinear behavior.
Fast Response Time: Varistors respond very quickly to voltage spikes and surges, providing prompt protection to sensitive electronic components.
Voltage Ratings: Varistors are available in a wide range of voltage ratings, allowing them to be used for various applications with different voltage levels.
Current Rating: Varistors can handle a certain amount of current, which is specified as the maximum peak current they can withstand without damage.
Operating Temperature Range: They have a specified operating temperature range within which they function optimally and offer effective protection.
Leakage Current: Varistors have a small amount of leakage current when subjected to lower voltage levels, but this is generally negligible.
Applications of Varistors:
Surge Protection: The primary application of varistors is in surge protection circuits. They are used to protect electronic devices from voltage spikes caused by lightning strikes, power surges, or electromagnetic interference. Varistors quickly divert excess voltage away from sensitive components, preventing damage.
Voltage Regulation: Varistors can be employed in voltage regulation circuits to maintain a relatively stable voltage level by shunting excess voltage when it exceeds a certain threshold.
Transient Voltage Suppression (TVS): Varistors are widely used as TVS devices in communication systems, power supplies, and data lines to suppress transient voltages and protect sensitive electronic components from damage.
Overvoltage Protection: Various electrical and electronic systems use varistors for overvoltage protection. They safeguard equipment from voltage levels beyond their rated capacity.
Lightning Arresters: Varistors are integral components of lightning arresters installed in electrical power distribution systems and telecommunication networks to protect against lightning-induced surges.
Power Surge Protectors: In surge protectors and power strips, varistors are used to safeguard connected devices from voltage spikes that may occur due to utility grid fluctuations or lightning strikes.
Electronic Circuits: Varistors can be used in various electronic circuits to provide voltage-dependent resistance and filtering applications.
It's important to note that while varistors are effective in handling voltage surges, they are not designed for continuous overvoltage conditions. If subjected to sustained high voltages, they may degrade or fail, so it's essential to use them within their specified limits and in conjunction with other protective measures for comprehensive surge protection.