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An inrush current limiter is a component used to limit inrush current to avoid gradual damage to components and avoid tripping the supply's fuse or circuit breaker. Negative temperature coefficient (NTC) thermistors and fixed resistors are often used to limit inrush current. NTC thermistors can be used as inrush-current limiting devices in power supply circuits when placed in series with the circuit being protected. They present a higher resistance initially, which prevents large currents from flowing at turn-on. As current continues to flow, NTC thermistors heat up, allowing higher current flow during normal operation. NTC thermistors are usually much larger than measurement type thermistors, and are purposely designed for power applications. ==Thermistor== An NTC thermistor's resistance is high at low temperatures. When the circuit is closed, the thermistor's resistance limits the initial current. After some time current flow heats the thermistor, and its resistance changes to a lower value, allowing current to flow uninterrupted. It is inherently impossible for 100% of supply voltage to appear on the protected circuit, as the thermistor must continue to dissipate power (producing heat) in order to maintain a low resistance. The resulting voltage drop from the operating resistance, and the power consumption of the thermistor must be taken into account. * Inrush current limiting thermistors are usually disk-shaped, with a radial lead on each side. * NTC resistor power handling is proportional to its size. * NTC resistors are rated according to their resistance at room temperature. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Inrush current limiter」の詳細全文を読む スポンサード リンク
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