Wyniki 1-1 spośród 1 dla zapytania: authorDesc:"Waldemar S. CHMIELAK"

Experimental research on time-current characteristics of fuses - initial results DOI:10.15199/48.2019.03.15

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Fuses, both with circuit breakers, are mainly used in electrical systems for protection against over-currents and other electrical faults. Depending on an application they can be used as a protection for cables or distribution feeders, transformers, induction motors, rectifiers etc. For the proper selection of a fuse, there have to be taken into consideration [1,4]: - Rated voltage, current and frequency - AC and DC service and type of a load current - Time-current and time versus I2t characteristics - Rated breaking capacity - Rated power dissipation of the fuse - Cut-off current in AC service. - Pre-arcing and arcing times - Dimensions. During normal system conditions the fuse works as a short-circuited. For over-current, depending on time, the fuse element will melt and the current will be switched off. The operation of blowing of a fuse element follows the sequence [1,4]: - For a specified amount of heat, the fuse element melts - Gap along the fuse element is formed during melting. - Arc is established across each gap. - The heat of arc further melts the ends of the element at each gap increasing it. - The arc quenches. The performance capabilities of fuses and be graphically represented by two types of fuse characteristic curves: time-current curves and peak let-through charts. These elements define the operating characteristics of a given fuse, and help in selecting the proper apparatus to protect equipment and electrical systems. On Fig. 1 the sample of a time-current curves for typical time-delay fuse series was presented. This characteristic describes the dependence of time which elapses for the moment when over current Iov appears till the moment when fuse element melt. This highly non-linear curves characterize protection abilities of an apparatus and are used for selection proper selectivity level. It is worth to point out, that thermal pr[...]

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