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NTC thermistors can be used as inrush-current limiting devices in power supply circuits when added 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.
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).
Current limiting reactor. The main motive of using current limiting reactors is to reduce short-circuit currents so that circuit breakers with lower short circuit breaking capacity can be used. They can also be used to protect other system components from high current levels and to limit the inrush current when starting a large motor. [5]
Inrush current, input surge current, or switch-on surge is the maximal instantaneous input current drawn by an electrical device when first turned on. Alternating-current electric motors and transformers may draw several times their normal full-load current when first energized, for a few cycles of the input waveform.
An NTC is commonly used as a temperature sensor, or in series with a circuit as an inrush current limiter. With PTC thermistors, resistance increases as temperature rises; usually because of increased thermal lattice agitations, particularly those of impurities and imperfections.
When used as protection devices, they shunt the current created by the excessive voltage away from sensitive components when triggered. The name varistor is a portmanteau of varying resistor. The term is only used for non-ohmic varying resistors. Variable resistors, such as the potentiometer and the rheostat, have ohmic characteristics.
Resettable fuse or PolySwitch – circuit breaker action using solid state device; Ground-fault protection or residual-current device – circuit breaker sensitive to mains currents passing to ground; Metal oxide varistor (MOV), surge absorber, TVS – Over-voltage protection; Inrush current limiter – protection against initial Inrush current
The recommended minimum operating current is only 35 μA (standard TL431: 1 mA); the maximum I CA and V CA are the same as standard (100 mA and 36 V). [50] Unity gain frequency is reduced to 250 kHz to attenuate high frequency ripples so they are not fed back to the controller. The ATL431 has a very different instability area. [50]