A Varistor (Varistor) is an electrical component that works primarily by changing its resistance value as the applied voltage changes. In general, the resistance of a varistor is larger at low voltage, but significantly reduced at high voltage, with overvoltage protection. Varistors are widely used to protect circuits from transient overvoltages (such as lightning strikes, surge currents, etc.).

The main role of varistor:
  Overvoltage protection:
      Suppression of surge current: Varistors can effectively absorb and suppress transient overvoltages caused by lightning, switching operation, or power system failures, protecting other components in the circuit from damage.
      Limit voltage rise: When the voltage exceeds the operating voltage of the varistor, its resistance value decreases sharply, causing most of the voltage to flow through the resistance to the ground, thus limiting the voltage to rise to a safe level.

Protect sensitive electronic components:
  Protection circuit components: In electronic devices, many components such as integrated circuits, microprocessors, etc., are very sensitive to voltage. Varistors prevent these sensitive elements from being burned or damaged by limiting excessive voltages.

Prevent electrical fires:
  Reducing voltage hazards: Varistors reduce the risk of damage to electrical equipment by reducing the impact of transient overvoltage on the circuit, thereby reducing the probability of electrical fires.
  
Electrical noise suppression:
  Reduce interference: varistor helps to reduce electrical noise in the power system, especially in the suppression of high-frequency noise, to provide a more stable power supply voltage, to ensure the normal operation of electronic equipment.
  
Lightning Strikes and Power Surge Protection:
  Application in power line protection: Varistors are widely used in power lines, telephone lines and other communication lines as lightning strikes and power surge protection devices to prevent instantaneous high voltage damage to connected equipment.
  
Improve system reliability:
  Improved equipment life: By limiting the impact of overvoltage, varistors can improve the reliability and service life of electronic devices. Long-term exposure to excessive voltage will accelerate the aging of equipment, and the use of varistors can effectively delay this process.
  
The working principle of varistor:
  At low voltage: the resistance value of the varistor is very large, almost non-conductive, and current cannot pass through.
  High voltage: When the applied voltage exceeds a certain threshold, the resistance of the varistor rapidly decreases and begins to conduct electricity, directing excess current to the ground and protecting the circuit from damage.
  
Common application areas:
  Power protection: such as UPS, switching power supply, power equipment, etc.
  Household appliances: such as air conditioning, TV, refrigerator, etc., to prevent overvoltage damage to electrical appliances.
  Communication equipment: such as telephones, network equipment, etc., to prevent equipment failures caused by power surges.
  Automotive electronics: Protects automotive circuits from voltage surges.