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Electric power distribution systems include circuit breakers to disconnect power in case of a fault, but to maximize reliability, they wish to disconnect the smallest possible portion of the network. This means that even the smallest circuit breakers, as well as all wiring to them, must be able to disconnect large fault currents. [citation needed]
In an electric power system, a fault or fault current is any abnormal electric current. For example, a short circuit is a fault in which a live wire touches a neutral or ground wire. An open-circuit fault occurs if a circuit is interrupted by a failure of a current-carrying wire (phase or neutral) or a blown fuse or circuit breaker.
Arc flash will be minimized if a pre-charge function slows down the activation time of a high voltage power-up. A slow pre-charge will also reduce the voltage into a faulty circuit which builds up while the system diagnostics come on-line. This allows a diagnostic shut down before the fault is fully realized in worst case proportions.
For example, the power-handling ability of a resistor may be greatly derated when applied in high-altitude aircraft to obtain adequate service life. A sudden fail-open fault can cause multiple secondary failures if it is fast and the circuit contains an inductance ; this causes large voltage spikes , which may exceed 500 volts.
A bricked device may not power on at all, or it may power on, but never boot to the OS or firmware, the closest getting to a warning screen. Some kernel bugs [ ambiguous ] have been known that affect the /data partition in the eMMC chip, which becomes corrupted during certain operations such as wiping and flashing.
A small circuit breaker typically has a manual control lever to switch the circuit off or reset a tripped breaker, while a larger unit may use a solenoid to trip the mechanism, and an electric motor to restore energy to springs (which rapidly separate contacts when the breaker is tripped).
A residual-current device (RCD), residual-current circuit breaker (RCCB) or ground fault circuit interrupter (GFCI) [a] is an electrical safety device, more specifically a form of Earth-leakage circuit breaker, that interrupts an electrical circuit when the current passing through line and neutral conductors of a circuit is not equal (the term residual relating to the imbalance), therefore ...
The purpose of selectivity is to minimize the impact of a failure on the network. Faults in an installation are, for example, overload and short circuit. [1] [2] There are four ways in which selectivity is achieved: [3] Current selectivity: different breaking capacities; Time selectivity: time delay before tripping of a breaker