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An inrush current limiter is a component used to limit inrush current to avoid gradual damage to components and avoid blowing fuses or tripping circuit breakers.Negative temperature coefficient (NTC) thermistors and fixed resistors are often used to limit inrush current.
An inrush current limiter is a device or devices combination used to limit inrush current. Passive resistive components such as resistors (with power dissipation drawback), or negative temperature coefficient (NTC) thermistors are simple options while the positive one (PTC) is used to limit max current afterward as the circuit has been operating (with cool-down time drawback on both).
The dynamics of PTC thermistors being powered lends to a wide range of applications. When first connected to a voltage source, a large current corresponding to the low, cold, resistance flows, but as the thermistor self-heats, the current is reduced until a limiting current (and corresponding peak device temperature) is reached.
Another type of thermal switch is a PTC (Positive Temperature Coefficient) thermistor; these thermistors have a "cutting off" temperature at which the resistance suddenly rises rapidly, limiting the current through the circuit. When used in conjunction with a thermistor relay, the PTC will switch off an electrical system at a desired temperature.
PTC heating elements also can be regulated indirectly. For example, a PTC heating element with a sharp change in resistance at a particular temperature can be fitted with a constant voltage source and a variable-speed fan. With the fan at a low setting, the heating element draws only a small amount of current, resulting in a low heat output.
With the PC industry rising from the 1980s in Taiwan, its NTC thermistor is adapted as the inrush current limiter in switched-mode power supply to suppress the inrush current when power supply turns on, and the varistor protects the circuit from damaged by surge current occasionally occurred in the electricity network.
The trip current is the current at which the device is guaranteed to trip. [7] When power is removed, the heating due to the leakage current will stop and the PPTC device will cool. As the device cools, it regains its original crystalline structure and returns to a low resistance state where it can hold the current as specified for the device. [6]
Below 2 Amperes, a variety of transient suppressing electronic components have been employed with varying success as arc suppressors, including: capacitors, snubbers, diodes, Zener diodes, transient voltage suppressors (TVS), resistors, varistors or in-rush current limiters (PTC and NTC resistors). [9]