PTC thermistor

PTC thermistor

The PTC thermistor is a composite PTC thermistor with dual protection functions of overvoltage and overcurrent protection. The PTC thermistor with overcurrent protection function and the varistor with overvoltage protection function are packaged into a device, making them Inter-coupling has both over-current protection and over-voltage protection. These products have been widely used in smart meters, high-performance small switching power supplies, and LED lighting applications, which have produced good economic and social benefits.

  1. Application: PTC thermistor is a protection element that automatically protects and restores abnormal temperature and abnormal current. It replaces traditional fuses and can be widely used for overcurrent and overload protection of motors, transformers, and electronic circuits. . The thermistor reduces the residual current value by limiting the consumption in the entire line through its sudden change of resistance value. In the traditional fuse line, it cannot recover by itself, but the PTC thermistor can restore its protection function after the fault is removed. .
Select a PTC thermistor as an overload protection element, first confirm the maximum normal working current of the line (that is, the non-operating current of the PTC thermistor) and the maximum ambient temperature of the PTC thermistor installation location (during normal operation), followed by protection The current (that is, the operating current of the PTC thermistor), the maximum operating voltage, the rated zero power resistance, and the external dimensions of the component should also be considered. As shown in the figure below: the relationship between the use of ambient temperature, non-operating current and operating current.
2. Scope of application: Mainly used for over-current, overload, short-circuit protection of smart meters, transformers, motors, switching power supplies, chargers, adapters, instruments, control panels, household appliances, air conditioners, microwave ovens, etc.

3. Application principle:
The over-current protection and over-voltage protection type PTC thermistor are connected in series in the power circuit. When the circuit is in a normal state, the current flowing through the PTC is less than the rated current, and the PTC is in a normal state, and the resistance value is small, which will not affect electronic equipment, etc. Normal operation of the protection circuit. When the circuit current greatly exceeds the rated current, the PTC suddenly heats up, and the resistance value suddenly increases to a high resistance state, thereby limiting or blocking the current and protecting the circuit from damage. After the current returns to normal, the PTC also automatically returns to the low-impedance state, and the circuit resumes normal work. Similarly, when the external voltage fluctuates, the varistor plays an over-voltage protection function, so that the increase in the current flowing through the PTC thermistor can also make the PTC suddenly heat up, and the resistance value suddenly increases to a high-impedance state, thereby limiting or blocking the current and protecting the voltage. The thermistor and the subsequent circuit are not damaged. The overcurrent and overvoltage protection PTC thermistor has a wide range of applications in instruments.