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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 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).
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]
Some thermistors have decreasing resistance with temperature, while other types have increasing resistance with temperature. This allows them to be used for limiting current to cold circuits, e.g. for inrush current protection, or for limiting current to hot circuits, e.g. to prevent thermal runaway.
If the example circuit from before is used with a pre-charge circuit which limits the dV/dT to less than 600 volts per second, then the inrush current will be reduced from 670 amperes to 7 amperes. This is a "kinder and gentler" way to activate a high voltage DC power distribution system.
The current density inside round wire away from the influences of other fields, as function of distance from the axis is given by: [6]: 38 Current density in round wire for various skin depths. Numbers shown on each curve are the ratio of skin depth to wire radius. The curve shown with the infinity sign is the zero frequency (DC) case.
Asymptotic analysis is a key tool for exploring the ordinary and partial differential equations which arise in the mathematical modelling of real-world phenomena. [3] An illustrative example is the derivation of the boundary layer equations from the full Navier-Stokes equations governing fluid flow.