What Is A Varistor?
Key Takeaway
A varistor is an electronic component that protects circuits from voltage spikes. It works by changing its resistance with the applied voltage. When the voltage is within normal limits, the varistor has high resistance. If the voltage spikes, the varistor’s resistance drops, allowing it to absorb the excess energy and protect the circuit. Varistors are commonly used in power strips, surge protectors, and various electronic devices. Understanding varistors helps in designing and maintaining safer electronic systems, preventing damage from unexpected voltage surges.
Definition and Function of Varistors
A varistor, also known as a voltage-dependent resistor (VDR), is an electronic component that protects circuits against excessive voltage. It has a non-linear resistance that varies with the applied voltage. When the voltage is low, the varistor has a high resistance, allowing minimal current flow. However, when the voltage exceeds a certain threshold, the resistance drops significantly, allowing higher current flow to shunt the excess voltage away from sensitive components. This ability to change resistance makes varistors crucial in safeguarding electronic circuits from voltage spikes and transient surges.
Types of Varistors
Varistors come in various types, each designed for specific applications, ensuring effective protection against voltage spikes. The most common type is the Metal Oxide Varistor (MOV). MOVs are widely used because of their excellent clamping capabilities and durability. These varistors are typically found in consumer electronics, power supplies, and telecommunications equipment, where they protect against transient voltage surges.
Another type is the Silicon Carbide Varistor. Known for its high energy absorption capability, this varistor is suitable for heavy industrial applications where robust protection is needed. Silicon Carbide Varistors are often used in environments that require handling significant surges and protecting large machinery.
Zinc Oxide Varistors are another important type. These are primarily used in high voltage applications, such as power distribution systems, due to their ability to handle large surge currents effectively. They are essential in ensuring the stability and reliability of electrical grids by protecting infrastructure from voltage spikes caused by lightning strikes or switching operations.
Understanding these types of varistors helps in selecting the appropriate one for specific protection needs. By choosing the right varistor, you can enhance the safety and durability of electronic devices and systems, making them resilient against unexpected voltage fluctuations.
How Varistors Protect Circuits
Varistors protect circuits by absorbing and dissipating excess energy from voltage spikes, a crucial function in maintaining the integrity of electronic systems. When a transient voltage surge occurs, such as from a lightning strike or a power line crossing, the varistor’s resistance decreases rapidly. This change allows the surge current to pass through the varistor instead of the protected circuit. By shunting the high voltage away, the varistor prevents the surge from reaching and potentially damaging sensitive components.
Once the surge subsides, the varistor returns to its high-resistance state, ready to protect against future surges. This ability to quickly respond to voltage changes and handle repeated surges makes varistors indispensable in many electronic protection schemes. They act as a first line of defense, ensuring that voltage spikes do not cause catastrophic failures in electronic devices.
The effectiveness of varistors in protecting circuits lies in their non-linear resistance properties, which allow them to absorb large amounts of energy without sustaining damage. This reliability and fast response time are why varistors are widely used in various applications, from consumer electronics to industrial machinery, providing robust protection against electrical transients.
Applications of Varistors
Varistors are essential in various applications to protect electronic devices and systems from voltage spikes. In consumer electronics, they safeguard everyday devices such as TVs, computers, and home appliances from power surges. These surges can be caused by events like lightning strikes or sudden power restorations, and varistors prevent damage by absorbing and dissipating the excess energy.
In industrial settings, varistors are crucial for protecting machinery and control systems from transient voltages. Industrial environments often involve heavy machinery and complex electrical systems, making them prone to voltage fluctuations. Varistors help ensure that these fluctuations do not cause malfunctions or damage, thereby maintaining operational efficiency and reducing downtime.
Telecommunications equipment also relies heavily on varistors. Sensitive circuitry in this equipment needs robust protection against lightning strikes and power surges to maintain reliable communication networks. Varistors play a key role in shielding these circuits from transient overvoltages.
Additionally, varistors are used in power supplies and distribution systems. They ensure stability and reliability by preventing transient overvoltages from disrupting operations. By integrating varistors, these systems can handle sudden voltage spikes without compromising performance or safety.
Overall, the versatility and reliability of varistors make them indispensable in a wide range of applications, providing essential protection for both consumer and industrial electronics.
Troubleshooting Varistor Issues
Troubleshooting varistor issues involves a systematic approach to ensure they function correctly and provide the necessary protection. Start with a visual inspection. Look for any signs of physical damage such as overheating, cracking, or burning. These indicators suggest that the varistor has absorbed a significant surge and might need replacement.
Next, test the varistor electrically using a digital multimeter. Begin by measuring its resistance. Under normal conditions, a good varistor should exhibit high resistance. When subjected to high voltage, the resistance should drop significantly. This change indicates that the varistor is functioning correctly. If the varistor shows low resistance at all times, it may be shorted and thus ineffective, requiring immediate replacement.
Performing these tests regularly as part of routine maintenance ensures that varistors continue to protect circuits effectively. If a varistor is found to be faulty, replace it promptly to maintain the integrity of your electrical protection scheme.
Regular inspections and testing not only ensure the varistor’s effectiveness but also enhance the overall reliability of the electrical system. This proactive approach minimizes the risk of unexpected failures and helps maintain continuous protection against voltage surges.
Conclusion
Varistors play a crucial role in protecting electrical and electronic systems from voltage spikes and surges. By rapidly changing resistance in response to overvoltage conditions, they divert harmful currents away from sensitive components, preventing damage and ensuring the longevity and reliability of electronic devices. Whether in consumer electronics, industrial machinery, or power distribution systems, the use of varistors enhances safety and stability. Understanding how to choose, use, and maintain varistors is essential for engineers and technicians to ensure effective circuit protection and overall system performance.