In modern industrial products, high-voltage large-capacity energy storage capacitors are increasingly used. They usually absorb huge currents when the system is started. This not only poses a threat to the rectifier devices and over-current fuses in the circuit, but may also cause harmonics to the public power grid. Wave pollution. The traditional solution is to use "cement resistors" with fixed resistance values as surge suppression components to limit the inrush current during startup. However, this solution has certain safety risks, especially in scenarios where resistors and relays are connected in parallel. Failure of the relay may cause continuous load current to flow through the high-resistance fixed resistor, resulting in high temperatures, smoke or even explosion. security issues.
To solve this problem, Huaju Electronics has launched a positive temperature coefficient ceramic thermistor PTC with surge suppression function. The resistance of PTC thermistor increases with temperature, which makes it have the function of self-protection. Under normal operating conditions, the low temperature and low resistance state of the PTC resistor allows current to pass smoothly. However, once the current increases abnormally, such as when a relay fails, the PTC resistor is heated, causing its resistance to increase rapidly, thereby reducing the flowing current, reducing thermal power, and preventing temperature runaway. This "resistance-temperature" positive correlation characteristic allows the PTC thermistor to maintain its temperature near the Curie temperature point (about 130 to 150°C) when a fault occurs, effectively avoiding the problem similar to traditional "cement". "Resistance" is an unsafe phenomenon caused by out-of-control temperature.
This excellent performance means that the PTC thermistor is not only able to protect itself during fault conditions, but also the downstream circuitry behind it. Moreover, once the relay fault is eliminated, the PTC thermistor can automatically return to its original low resistance state and continue to work normally. This self-recovery function greatly enhances the safety and reliability of the circuit.
In short, Huaju Electronics' PTC thermistor has shown great potential in charging protection of high-voltage large-capacity energy storage capacitors. Its unique positive temperature coefficient characteristic not only provides effective surge suppression, but also solves the safety problems of traditional fixed-value resistors. In the design of power electronic equipment, PTC thermistors, as a new surge suppression solution, will provide circuit designers with more choices and flexibility.