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Calculation of the required breaking capacity involves determining the supply impedance and voltage. Supply impedance is calculated from the impedance of the elements making up the supply system. Customers of an electrical supply utility can request the maximum value of prospective short-circuit current available at their point of supply.
This allows calculation by an industrial customer of its internal fault levels within its plant. If the prospective short-circuit current from the utility source is very large compared to the customer's system size, an "infinite bus" is assumed, with zero effective internal impedance; the only limit to the prospective short-circuit current is ...
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]
This latter figure is the ampere interrupting capacity (AIC) of the breaker. Under short-circuit conditions, the calculated or measured maximum prospective short-circuit current may be many times the normal, rated current of the circuit.
A short circuit is an abnormal connection between two nodes of an electric circuit intended to be at different voltages. This results in an electric current limited only by the Thévenin equivalent resistance of the rest of the network which can cause circuit damage, overheating, fire or explosion.
Breakdown voltage is a characteristic of an insulator that defines the maximum voltage difference that can be applied across the material before the insulator conducts. In solid insulating materials, this usually [citation needed] creates a weakened path within the material by creating permanent molecular or physical changes by the sudden current.
Lifting equipment can be assigned a Working Load Limit (WLL) in the interests of avoiding failure; Working Load Limit is calculated by dividing the Minimum Breaking Load of the equipment by a safety factor. [5] WLL as a concept is not restricted to lifting, being also relevant for mooring ropes. [6]
While glass fuses have the advantage of a fuse element visible for inspection purposes, they have a low breaking capacity (interrupting rating), which generally restricts them to applications of 15 A or less at 250 V AC. Ceramic fuses have the advantage of a higher breaking capacity, facilitating their use in circuits with higher current and ...